Light source device and projector

ABSTRACT

A light source device includes a light source, a first polarization split element for transmitting first light from the light source which is polarized in a first polarization direction and reflecting the first light polarized in a second polarization direction, a first optical element for reflecting the first light from the first polarization split element, a diffusion element for diffusing the first light from the first polarization split element, a wavelength conversion element for performing wavelength conversion on the first light from the first optical element to emit second light, a second polarization split element which the second light enters from the first optical element, and which transmits the second light polarized in the first polarization direction and reflects the second light polarized in the second polarization direction, and a second optical element for reflecting the second light from the second polarization split element, polarized in the second polarization direction.

The present application is based on, and claims priority from JPApplication Serial Number 2020-156176, filed Sep. 17, 2020, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a light source device and a projector.

2. Related Art

There has been known a projector which modulates light emitted from alight source to generate image light based on image information, andthen projects the image light thus generated. In JP-A-4-60538 (Document1), there is disclosed a projection type color image display deviceprovided with a light source, a plurality of dichroic mirrors, a liquidcrystal display element having a microlens array, and a projection lens.The projection type color image display device separates the white lightemitted from the light source into a plurality of colored light beamshaving respective colors different from each other, and then makes thecolored light beams thus separated from each other enter the respectivesub-pixels different from each other in one liquid crystal displayelement to thereby perform color display.

In the projection type color image display device described above, thereare arranged a red reflecting dichroic mirror, a green reflectingdichroic mirror, and a blue reflecting dichroic mirror along theincident light axis of the white light emitted from the light source ina state of being nonparallel to each other. The white light emitted fromthe light source passes through the dichroic mirrors described above tothereby be separated into red light, green light, and blue lightdifferent in proceeding direction from each other. The red light, thegreen light, and the blue light respectively enter red sub-pixels, greensub-pixels, and blue sub-pixels of the light modulation element in thestate of being spatially separated from each other by a microlensdisposed at the incidence side of the light modulation element.

In the projection type color image display device in Document 1, a lamplight source such as a halogen lamp or a xenon lamp is adopted as thewhite light source, and a liquid crystal display element is adopted asthe light modulation element. Although the light emitted from the lamplight source is unpolarized light, when using the liquid crystal displayelement as the light modulation element, the light entering the liquidcrystal display element needs to be linearly polarized light having aspecific polarization direction. To this end, it is conceivable todispose a pair of multi-lens arrays for dividing the incident light intoa plurality of partial light beams, and a polarization conversionelement for uniforming the polarization directions of the plurality ofpartial light beams between the white light source and the liquidcrystal display element as a device for homogenously illuminating theliquid crystal display element. In this case, there is generally used apolarization conversion element provided with a plurality ofpolarization split layers and a plurality of reflecting layersalternately arranged along a direction crossing the incident directionof the light, and a retardation layer disposed in a light path of thelight transmitted through the polarization split layers or a light pathof the light reflected by the reflecting layers.

However, when reducing the projection type color image display devicedescribed above in size in compliance with the recent demand ofreduction in size, it is difficult to manufacture the polarizationconversion element narrow in pitch between the polarization split layerand the reflecting layer. Therefore, it is difficult to reduce the sizeof the light source device equipped with this type of polarizationconversion element, and by extension, to reduce the size of theprojector equipped with the light source device. In view of such aproblem, it is required to provide a light source device capable ofemitting a plurality of colored light beams uniformed in polarizationdirection without using the polarization conversion element narrow inpitch.

SUMMARY

In view of the problems described above, a light source device accordingto an aspect of the present disclosure includes a light source sectionconfigured to emit a first light beam which has a first wavelength bandand includes light polarized in a first polarization direction and lightpolarized in a second polarization direction different from the firstpolarization direction, a first polarization split element which isconfigured to transmit the first light beam entering the firstpolarization split element from the light source section along a firstdirection and polarized in the first polarization direction toward thefirst direction, and is configured to reflect the first light beampolarized in the second polarization direction toward a second directioncrossing the first direction, a first optical element disposed at thefirst direction side of the first polarization split element, andconfigured to reflect the first light beam which enters the firstoptical element along the first direction from the first polarizationsplit element toward the second direction, a diffusion element disposedat the second direction side of the first polarization split element,and configured to diffuse the first light beam which enters thediffusion element along the second direction from the first polarizationsplit element, and emit the first light beam diffused toward a thirddirection as an opposite direction to the second direction, a wavelengthconversion element disposed at the second direction side of the firstoptical element, configured to perform wavelength conversion on thefirst light beam which enters the wavelength conversion element alongthe second direction from the first optical element, and configured toemit a second light beam having a second wavelength band different fromthe first wavelength band toward the third direction, a secondpolarization split element which is disposed at the third direction sideof the first optical element, which the second light beam enters alongthe third direction from the first optical element, and which isconfigured to transmit the second light beam polarized in the firstpolarization direction toward the third direction, and reflect thesecond light beam polarized in the second polarization direction towarda fourth direction as an opposite direction to the first direction, anda second optical element disposed at the fourth direction side of thesecond polarization split element, and configured to reflect the secondlight beam which enters the second optical element along the fourthdirection from the second polarization split element, and is polarizedin the second polarization direction, toward the third direction,wherein the first polarization split element transmits the first lightbeam which enters the first polarization split element along the thirddirection from the diffusion element toward the third direction, thefirst optical element transmits the second light beam which enters thefirst optical element along the third direction from the wavelengthconversion element toward the third direction, and the second opticalelement transmits the first light beam which enters the second opticalelement along the third direction from the first polarization splitelement toward the third direction.

A light source device according to another aspect of the presentdisclosure includes a light source section configured to emit a firstlight beam which has a first wavelength band and includes lightpolarized in a first polarization direction and light polarized in asecond polarization direction different from the first polarizationdirection, a first polarization split element which is configured totransmit the first light beam entering the first polarization splitelement from the light source section along a first direction andpolarized in the first polarization direction toward the firstdirection, and is configured to reflect the first light beam polarizedin the second polarization direction toward a second direction crossingthe first direction, a first optical element disposed at the firstdirection side of the first polarization split element, and configuredto reflect the first light beam which enters the first optical elementalong the first direction from the first polarization split elementtoward the second direction, a diffusion element disposed at the seconddirection side of the first optical element, and configured to diffusethe first light beam which enters the diffusion element along the seconddirection from the first optical element, and emit the first light beamdiffused toward a third direction as an opposite direction to the seconddirection, a wavelength conversion element disposed at the seconddirection side of the first polarization split element, configured toperform wavelength conversion on the first light beam which enters thewavelength conversion element along the second direction from the firstpolarization split element, and configured to emit a second light beamhaving a second wavelength band different from the first wavelength bandtoward the third direction, a second polarization split element which isdisposed at the third direction side of the first polarization splitelement, which the second light beam enters along the third directionfrom the first polarization split element, and which is configured totransmit the second light beam polarized in the first polarizationdirection toward the third direction, and reflect the second light beampolarized in the second polarization direction toward the firstdirection, and a second optical element disposed at the first directionside of the second polarization split element, and configured to reflectthe second light beam which enters the second optical element along thefirst direction from the second polarization split element, and ispolarized in the second polarization direction, toward the thirddirection, wherein the first optical element transmits the first lightbeam which enters the first optical element along the third directionfrom the diffusion element toward the third direction, the firstpolarization split element transmits the second light beam which entersthe first polarization split element along the third direction from thewavelength conversion element toward the third direction, and the secondoptical element transmits the first light beam which enters the secondoptical element along the third direction from the first optical elementtoward the third direction.

A projector according to an aspect of the present disclosure includesthe light source device according to the aspect of the presentdisclosure, a light modulation device configured to modulate light fromthe light source device in accordance with image information, and aprojection optical device configured to project the light modulated bythe light modulation device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram of a projector according toa first embodiment.

FIG. 2 is a perspective view of a light source device according to thefirst embodiment.

FIG. 3 is a plan view of the light source device viewed from a +Ydirection.

FIG. 4 is a side view of the light source device viewed from a −Xdirection.

FIG. 5 is a side view of the light source device viewed from a +Xdirection.

FIG. 6 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

FIG. 7 is an enlarged view of a light modulation device.

FIG. 8 is a side view of a light source device according to a secondembodiment viewed from the −X direction.

FIG. 9 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

FIG. 10 is a plan view of a light source device according to a thirdembodiment viewed from the +Y direction.

FIG. 11 is a side view of the light source device viewed from the −Xdirection.

FIG. 12 is a side view of the light source device viewed from the +Xdirection.

FIG. 13 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

FIG. 14 is a side view of a light source device according to a fourthembodiment viewed from the −X direction.

FIG. 15 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A first embodiment of the present disclosure will hereinafter bedescribed using FIG. 1 through FIG. 7.

FIG. 1 is a schematic configuration diagram of a projector 1 accordingto the present embodiment.

It should be noted that in each of the drawings described below, theconstituents are shown with the scale ratios of respective sizes setdifferently between the constituents in some cases in order to make eachof the constituents eye-friendly.

The projector 1 according to the present embodiment modulates the lightemitted from a light source device 2 to form an image corresponding toimage information, and then projects the image thus formed on aprojection target surface such as a screen in an enlarged manner. Inother words, the projector 1 modulates the light emitted from the lightsource device 2 with a single light modulation device 6 including asingle liquid crystal panel 61 to thereby form the image, and thenprojects the image thus formed. The projector 1 is a so-calledsingle-panel projector.

As shown in FIG. 1, the projector 1 is provided with the light sourcedevice 2, a homogenization device 4, a field lens 5, the lightmodulation device 6, and a projection optical device 7. The light sourcedevice 2, the homogenization device 4, the field lens 5, the lightmodulation device 6, and the projection optical device 7 are disposed atpredetermined positions along an illumination light axis Ax. Theillumination light axis Ax is defined as an axis along the proceedingdirection of the principal ray of the light L emitted from the lightsource 2.

The configuration of the light source device 2 and the homogenizationdevice 4 will be described later in detail.

The field lens 5 is disposed between the homogenization device 4 and thelight modulation device 6. The field lens 5 collimates the light Lemitted from the homogenization device 4, and then guides the result tothe light modulation device 6.

The projection optical device 7 projects the light modulated by thelight modulation device 6, namely the light forming the image, on theprojection target surface (not shown) such as a screen. The projectionoptical device 7 has a single projection lens or a plurality ofprojection lenses.

In the following description, the axis parallel to the proceedingdirection of the light emitted from the light source device 2 along theillumination light axis Ax is defined as a Z axis, and the proceedingdirection of the light is defined as a +Z direction. Further, two axeseach perpendicular to the Z axis, and perpendicular to each other aredefined as an X axis and a Y axis. Out of the directions along theseaxes, an upper side in the vertical direction in the space in which theprojector 1 is installed is defined as a +Y direction. Further, theright side in the horizontal direction when viewing an object which thelight enters along the +Z direction so that the +Y direction points theupper side in the vertical direction is defined as a +X direction.Although not shown in the drawings, an opposite direction to the +Xdirection is defined as a −X direction, an opposite direction to the +Ydirection is defined as a −Y direction, and an opposite direction to the+Z direction is defined as a −Z direction.

The +X direction in the present embodiment corresponds to a firstdirection in the appended claims. The −Z direction in the presentembodiment corresponds to a second direction in the appended claims. The+Z direction in the present embodiment corresponds to a third directionin the appended claims. The −X direction in the present embodimentcorresponds to a fourth direction in the appended claims.

Configuration of Light Source Device

FIG. 2 is a perspective view of the light source device 2 according tothe present embodiment. FIG. 3 is a plan view of the light source device2 viewed from the +Y direction.

As shown in FIG. 2 and FIG. 3, the light source device 2 emits the lightL for illuminating the light modulation device 6 toward a directionparallel to the illumination light axis Ax, namely the +Z direction. Thelight L emitted by the light source device 2 includes a plurality ofcolored light beams which are linearly polarized light beams having auniform polarization direction, and are spatially separated from eachother. In the present embodiment, the light L emitted by the lightsource device 2 consists of four light beams each formed of S-polarizedlight. The four light beams correspond to a blue light beam BLs, ayellow light beam YLs, a green light beam GLs, and a red light beam RLs.

The light source device 2 is provided with a light source section 21, afirst polarization split element 51, a third retardation element 54, afirst optical element 52, a second polarization split element 23, asecond optical element 22, a first retardation element 24, a first lightcollection element 25, a diffusion device 26, a second light collectionelement 27, a wavelength conversion element 28, a fourth retardationelement 32, a first color separation element 29, a fifth retardationelement 30, a reflecting element 31, and a second color separationelement 33.

It should be noted that the P-polarized light in the present embodimentcorresponds to light polarized in a first polarization direction in theappended claims. The S-polarized light in the present embodimentcorresponds to light polarized in a second polarization direction in theappended claims. Further, as described later, the first polarizationsplit element 51, the first optical element 52, the second polarizationsplit element 23, and the second optical element 22 are different inorientation of a film for separating the polarization components orcolored light beams from the first color separation element 29 and thesecond color separation element 33. Therefore, the descriptions ofP-polarized light and S-polarized light in the present embodimentrepresent the polarization direction with respect to the firstpolarization split element 51, the first optical element 52, the secondpolarization split element 23, and the second optical element 22, andare reversed in the polarization direction with respect to the firstcolor separation element 29 and the second color separation element 33.

In other words, the P-polarized light with respect to the firstpolarization split element 51, the first optical element 52, the secondpolarization split element 23, and the second optical element 22corresponds to the S-polarized light with respect to the first colorseparation element 29 and the second color separation element 33. TheS-polarized light with respect to the first polarization split element51, the first optical element 52, the second polarization split element23, and the second optical element 22 corresponds to the P-polarizedlight with respect to the first color separation element 29 and thesecond color separation element 33. It should be noted that since thereis a possibility that the description gets confusing when changing thename of one type of light in accordance with the element which thepolarized light enters, the P-polarized light and the S-polarized lightare hereinafter described as the polarization direction with respect tothe first polarization split element 51, the first optical element 52,the second polarization split element 23, and the second optical element22 without changing the name of the polarized light in accordance withthe element which these types of polarized light enter.

Further, in each of the drawings, the P-polarized light is representedby a dotted-line arrow, the S-polarized light is represented by a solidarrow, and light in other polarization states than the P-polarized lightand the S-polarized light is represented by a dashed-dotted-line arrow.

Configuration of Light Source Section

The light source section 21 emits the blue light beams BLs, BLp whichenter the first polarization split element 51 along the +X direction.The light source section 21 has a plurality of light emitting elements211, a plurality of collimator lenses 212, and a rotary retardationdevice 213. The light emitting elements 211 are each formed of asolid-state light source for emitting the blue light beam BLs.Specifically, the light emitting elements 211 are each formed of asemiconductor laser for emitting the blue light beam BLs as theS-polarized light. The blue light beam BLs is a laser beam having a bluewavelength band of, for example, 440 through 480 nm, and having a peakwavelength within a range of, for example, 450 through 460 nm. The bluewavelength band in the present embodiment corresponds to a firstwavelength band in the appended claims. The blue light beams BLs, BLp inthe present embodiment correspond to a first light beam in the appendedclaims.

In the case of the present embodiment, the plurality of light emittingelements 211 is arranged along the Z axis. Although the light sourcesection 21 in the present embodiment has two light emitting elements211, the number of the light emitting elements 211 is not limited, andthe number of the light emitting elements 211 can be one. Further, thearrangement of the plurality of light emitting elements 211 is notlimited as well. Further, the light emitting elements 211 are arrangedso as to emit the blue light beams BLs as the S-polarized light, but canbe arranged so as to emit the blue light beams as the P-polarized lightsince a light intensity ratio between the S-polarized light and theP-polarized light can arbitrarily be set by the rotary retardationdevice 213. In other words, it is possible for the light emittingelements 211 to rotate as much as 90° centering on the emission opticalaxis.

The plurality of collimator lenses 212 is disposed between the pluralityof light emitting elements 211 and the rotary retardation device 213.The collimator lenses 212 are disposed so as to correspond one-to-one tothe light emitting elements 211. The collimator lens 212 collimates thelight beam BLs emitted from the light emitting element 211.

The rotary retardation device 213 has a second retardation element 2131,and a rotation device 2132. The second retardation element 2131 is maderotatable centering on a rotational axis along a proceeding direction ofthe light entering the second retardation element 2131, namely arotational axis parallel to the X axis. The rotation device 2132 isformed of a motor and so on, and rotates the second retardation element2131.

The second retardation element 2131 is formed of a ½ wave plate or a ¼wave plate with respect to the blue wavelength band. A part of the bluelight beam BLs as the S-polarized light having entered the secondretardation element 2131 is converted into the blue light beam BLp asthe P-polarized light by the second retardation element 2131. Therefore,the blue light beam having been transmitted through the secondretardation element 2131 turns to light in which the blue light beam BLsas the S-polarized light and the blue light beam BLp as the P-polarizedlight mixed with each other with a predetermined ratio. Specifically,the blue light beams BLs as the S-polarized light emitted from the lightemitting elements 211 enter the second retardation element 2131, and theblue light including the blue light beam BLs as the S-polarized lightand the blue light beam BLp as the P-polarized light is emitted from thesecond retardation element 2131.

By the rotation device 2132 adjusting the rotational angle of the secondretardation element 2131, there is adjusted the ratio between the lightintensity of the blue light beam BLs as the S-polarized light includedin the light beam having been transmitted through the second retardationelement 2131 and the light intensity of the blue light beam BLp as theP-polarized light included in the light beam having been transmittedthrough the second retardation element 2131. It should be noted thatwhen there is no need to adjust the ratio between the light intensity ofthe blue light beam BLs and the light intensity of the blue light beamBLp, the rotation device 2132 for rotating the second retardationelement 2131 is not required to be disposed. In that case, therotational angle of the second retardation element 2131 is set so thatthe ratio between the light intensity of the blue light beam BLs and thelight intensity of the blue light beam BLp becomes a predetermined lightintensity ratio, and then the rotational position of the secondretardation element 2131 is fixed.

In such a manner, the light source section 21 emits the blue lightincluding the blue light beam BLs as the S-polarized light and the bluelight beam BLp as the P-polarized light. It should be noted that in thepresent embodiment, there is adopted the configuration in which all ofthe light emitting elements 211 emit the blue light beam BLs as theS-polarized light, but it is possible to adopt a configuration in whichthe light emitting element 211 for emitting the blue light beam BLs asthe S-polarized light and the light emitting element 211 for emittingthe blue light beam BLp as the P-polarized light are mixed. According tothis configuration, it is also possible to omit the rotary retardationdevice 213. Further, it is also possible for the light emitting element211 to be formed of another solid-state light source such as an LED(Light Emitting Diode) instead of the semiconductor laser.

Configuration of First Polarization Split Element

The blue light including the blue light beam BLs as the S-polarizedlight and the blue light beam BLp as the P-polarized light emitted fromthe light source section 21 enter the first polarization split element51 along the +X direction. Although the detailed illustration will beomitted, the first polarization split element 51 is constituted by asubstrate, and an optical film formed on one surface of the substrate.Specifically, the first polarization split element 51 according to thepresent embodiment is formed of a plate type optical element. Thesubstrate is formed of, for example, general optical glass. The opticalfilm is formed of, for example, a dielectric multilayer film.

The optical film has a characteristic of transmitting the P-polarizedlight and reflecting the S-polarized light with respect to the light inthe blue wavelength band. In other words, the optical film has apolarization split characteristic with respect to the blue light. Thesubstrate is disposed so as to be tilted 45° with respect to the X axisand the Z axis. In other words, the substrate is disposed so as to betilted 45° with respect to an X-Y plane and a Y-Z plane. Therefore, thefirst polarization split element 51 transmits the blue light beam BLp asthe P-polarized light which enters the first polarization split element51 along the +X direction from the light source section 21 toward the +Xdirection, and reflects the blue light beam BLs as the S-polarized lightwhich enters the first polarization split element 51 along the +Xdirection toward the −Z direction. Further, as described later, the bluelight beam BLp which enters the first polarization split element 51along the +Z direction from a diffusion plate 261 is transmitted by thefirst polarization split element 51 toward the +Z direction.

It should be noted that there is no chance for the yellow light beam YLemitted from the wavelength conversion element 28 to enter the firstpolarization split element 51. Therefore, it is sufficient for the firstpolarization split element 51 to have a polarization splitcharacteristic with respect to the light in the blue wavelength band,and the characteristic with respect to light in a wavelength bandincluding the green wavelength band and the red wavelength band is notlimited. Further, the first polarization split element 51 can beconstituted by two base members each having an isosceles righttriangular prismatic shape, and an optical film disposed between tiltedsurfaces opposed to each other of the two base members. Specifically,the first polarization split element 51 can be formed of a prism typeoptical element.

Configuration of Third Retardation Element

The third retardation element 54 is disposed at the +X direction side ofthe first polarization split element 51. In other words, the thirdretardation element 54 is disposed between the first polarization splitelement 51 and the first optical element 52 on the X axis. The thirdretardation element 54 is formed of a ½ wave plate with respect to theblue wavelength band which the blue light beam BLp emitted from thefirst polarization split element 51 has. Thus, the blue light beam BLpas the P-polarized light emitted along the +X direction from the firstpolarization split element 51 is converted by the third retardationelement 54 into the blue light beam BLs as the S-polarized light. Itshould be noted that in the present embodiment, the third retardationelement 54 is not necessarily required to be disposed.

Configuration of First Optical Element

The first optical element 52 is disposed at the +X direction side of thefirst polarization split element 51. The blue light beam BLs as theS-polarized light which has been emitted from the first polarizationsplit element 51, and the polarization direction of which has beenconverted by the third retardation element 54 enters the first opticalelement 52 along the +X direction. Although the detailed illustrationwill be omitted, the first optical element 52 is constituted by asubstrate, and an optical film formed on one surface of the substrate.Specifically, the first optical element 52 in the present embodiment isformed of a plate type optical element. The substrate is formed of, forexample, general optical glass. The optical film is formed of, forexample, a dielectric multilayer film.

The optical film has a characteristic of reflecting the S-polarizedlight with respect to the light in the blue wavelength band, andtransmitting light in a wavelength band including the green wavelengthband and the red wavelength band irrespective of the polarizationdirection. The substrate is disposed so as to be tilted 45° with respectto the X axis and the Z axis. In other words, the substrate is disposedso as to be tilted 45° with respect to the X-Y plane and the Y-Z plane.Therefore, the blue light beam BLs as the S-polarized light which entersthe first optical element 52 along the +X direction from the firstpolarization split element 51 is reflected by the first optical element52 toward the −Z direction. Further, the yellow light beam YL whichenters the first optical element 52 along the +Z direction from thewavelength conversion element 28 is transmitted by the first opticalelement 52 toward the +Z direction.

It should be noted that since it is sufficient for the first opticalelement 52 to reflect at least the S-polarized light with respect to thelight in the blue wavelength band, it is possible for the first opticalelement 52 to transmit the P-polarized light or to reflect theP-polarized light. Therefore, it is possible for the first opticalelement 52 to have a polarization split characteristic of reflecting theS-polarized light and transmitting the P-polarized light with respect tothe light in the blue wavelength band, and a characteristic oftransmitting the light in the wavelength band including the greenwavelength band and the red wavelength band. Alternatively, it ispossible for the first optical element to have a characteristic ofreflecting both of the S-polarized light and the P-polarized light withrespect to the light in the blue wavelength band, and transmitting thelight in the wavelength band including the green wavelength band and thered wavelength band.

In the case of the present embodiment, since the third retardationelement 54 is provided, the blue light beam BLs as the S-polarized lightenters the first optical element 52. Therefore, it is possible for thefirst optical element 52 to have any one of the two types ofcharacteristic described above. It should be noted that when the thirdretardation element 54 is not provided unlike the configuration of thepresent embodiment, the blue light beam BLp as the P-polarized lighthaving been transmitted through the first polarization split element 51directly enters the first optical element 52. Therefore, it is necessaryfor the first optical element 52 to reflect the P-polarized light withrespect to the light in the blue wavelength band. In this case, it issufficient for the first optical element 52 to be formed of a dichroicmirror for reflecting the light in the blue wavelength band, andtransmitting the light in the wavelength band including the greenwavelength band and the red wavelength band.

Configuration of Second Polarization Split Element

The second polarization split element 23 is disposed at the +Z directionside of the first optical element 52. The yellow light beam YL havingbeen transmitted through the first optical element 52 enters the secondpolarization split element 23 along the +Z direction. The secondpolarization split element 23 is formed of a prism type polarizationsplit element. The second polarization split element 23 has two basemembers 232 and a polarization split layer 231 disposed between the twobase members 232.

Specifically, each of the two base members 232 has a substantiallyisosceles right triangular prismatic shape. The two base members 232 arecombined with each other so that the tilted surfaces are opposed to eachother, and are formed to have a substantially rectangular solid shape asa whole. The polarization split layer 231 is disposed between the tiltedsurfaces of the two base members 232. The polarization split layer 231is tilted 45° with respect to the X axis and the Z axis. In other words,the polarization split layer 231 is tilted 45° with respect to the X-Yplane and the Y-Z plane. Further, the polarization split layer 231 isdisposed in parallel to the first optical element 52.

The polarization split layer 231 has a polarization split characteristicof reflecting the S-polarized light and transmitting the P-polarizedlight with respect to the light in the wavelength band including thegreen wavelength band and the red wavelength band. Therefore, the yellowlight beam YL enters the second polarization split element 23 along the+Z direction from the first optical element 52, and the secondpolarization split element 23 transmits the yellow light beam YLp as theP-polarized light toward the +Z direction, and reflects the yellow lightbeam YLs as the S-polarized light toward the −X direction. Thepolarization split layer 231 is formed of, for example, a dielectricmultilayer film. The base members 232 are each formed of general opticalglass. It should be noted that there is no chance for the blue lightbeams BLp, BLs to enter the second polarization split element 23.Therefore, it is sufficient for the second polarization split element 53to have a polarization split characteristic with respect to the light inthe wavelength band including the green wavelength band and the redwavelength band, and the characteristic with respect to the light in theblue wavelength band is not limited.

Configuration of Second Optical Element

The second optical element 22 is disposed at the −X direction side ofthe second polarization split element 23. Further, the second opticalelement 22 is disposed at the +Z direction side of the firstpolarization split element 51. The yellow light beam YLs emitted fromthe second polarization split element 23 enters the second opticalelement 22 along the −X direction. Further, the blue light beam BLpemitted from the first polarization split element 51 enters the secondoptical element 22 along the +Z direction. The second optical element 22is formed of a prism type polarization split element. The second opticalelement 22 has two base members 222 and an optical layer 221 disposedbetween the two base members 222.

Specifically, each of the two base members 222 has a substantiallyisosceles right triangular prismatic shape. The two base members 222 arecombined with each other so that the tilted surfaces are opposed to eachother, and are formed to have a substantially rectangular solid shape asa whole. The optical layer 221 is disposed between the tilted surfacesof the two base members 222. The optical layer 221 is tilted 45° withrespect to the X axis and the Z axis. In other words, the optical layer221 is tilted 45° with respect to the X-Y plane and the Y-Z plane.Further, the optical layer 221 is disposed in parallel to thepolarization split layer 231 and the first polarization split element51.

The optical layer 221 has a characteristic of transmitting at least theP-polarized light with respect to the light in the blue wavelength band,and reflecting at least the S-polarized light with respect to the lightin the wavelength band including the green wavelength band and the redwavelength band. Thus, the yellow light beam YLs as the S-polarizedlight which enters the second optical element 22 along the −X directionfrom the second polarization split element 23 is reflected by the secondoptical element 22 toward the −X direction. Further, the blue light beamBLp as the P-polarized light which enters the second optical element 22along the +Z direction from the first polarization split element 51 istransmitted by the second optical element 22 toward the +Z direction.The optical layer 221 is formed of, for example, a dielectric multilayerfilm. The base members 222 are each formed of general optical glass.

It should be noted that since it is sufficient for the second opticalelement 22 to transmit at least the P-polarized light with respect tothe light in the blue wavelength band, it is possible for the secondoptical element to transmit the S-polarized light or to reflect theS-polarized light. Further, since it is sufficient for the secondoptical element 22 to reflect at least the S-polarized light withrespect to the light in the wavelength band including the greenwavelength band and the red wavelength band, it is possible for thesecond optical element 22 to transmit the P-polarized light or toreflect the P-polarized light. Therefore, it is possible for the secondoptical element 22 to have a polarization split characteristic oftransmitting the P-polarized light with respect to the light in the bluewavelength band, and transmitting the P-polarized light and reflectingthe S-polarized light with respect to the light in the wavelength bandincluding the green wavelength band and the red wavelength band.Alternatively, it is possible for the second optical element 22 to havea polarization split characteristic of transmitting the P-polarizedlight and reflecting the S-polarized light with respect to the light inthe entire wavelength band in the visible range.

Configuration of First Retardation Element

The first retardation element 24 is disposed at the −Z direction side ofthe first polarization split element 51. Specifically, the firstretardation element 24 is disposed between the first polarization splitelement 51 and the diffusion plate 261 on the Z axis. The firstretardation element 24 is formed of a ¼ wave plate with respect to theblue wavelength band of the blue light beam BLs which enters the firstretardation element 24. The blue light beam BLs as the S-polarized lighthaving been reflected by the first polarization split element 51 isconverted by the first retardation element 24 into, for example, a bluelight beam BLc1 as clockwise circularly polarized light, and is thenemitted toward the first light collection element 25. In such a manner,the blue light beam BLs as the S-polarized light emitted along the −Zdirection from the first polarization split element 51 enters the firstretardation element 24, and the first retardation element 24 convertsthe polarization state of the blue light beam BLs from the linearlypolarized light into the circularly polarized light.

Configuration of First Light Collection Element

The first light collection element 25 is disposed at the −Z directionside of the first retardation element 24. Specifically, the first lightcollection element 25 is disposed between the first retardation element24 and the diffusion plate 261 on the Z axis. The first light collectionelement 25 converges the blue light beam BLc1 which enters the firstlight collection element 25 from the first retardation element 24 on thediffusion plate 261. Further, the first light collection element 25collimates a blue light beam BLc2 described later which enters the firstlight collection element 25 from the diffusion plate 261, and then emitsthe result toward the first retardation element 24. In the example shownin FIG. 3, the first light collection element 25 is constituted by twoconvex lenses, namely a first lens 251 and a second lens 252. It shouldbe noted that the number of the lenses constituting the first lightcollection element 25 is not particularly limited.

Configuration of Diffusion Device

The diffusion device 26 is disposed at the −Z direction side of thefirst light collection element 25. In other words, the diffusion device26 is disposed at the −Z direction side of the first polarization splitelement 51. The diffusion device 26 diffuses the blue light beam BLc1which enters the diffusion device 26 along the −Z direction from thefirst polarization split element 51 via the first retardation element 24and the first light collection element 25 so that the diffusion anglebecomes equivalent to that of the yellow light beam YL which is emittedfrom the wavelength conversion element 28 described later, and thenemits the result toward the +Z direction.

The diffusion device 26 is provided with the diffusion plate 261 and arotation device 262. The diffusion plate 261 preferably has a reflectioncharacteristic as close to the Lambertian scattering as possible, andreflects the blue light beam BLc1 having entered the diffusion plate 261in a wide-angle manner. The rotation device 262 is formed of a motor andso on, and rotates the diffusion plate 261 centering on a rotationalaxis Rx parallel to the Z axis.

The diffusion plate 261 in the present embodiment corresponds to adiffusion element in the appended claims.

The blue light beam BLc1 having entered the diffusion plate 261 isreflected by the diffusion plate 261 to thereby be converted into theblue light beam BLc2 as circularly polarized light having an oppositerotational direction. In other words, the blue light beam BLc1 as theclockwise circularly polarized light is converted by the diffusion plate261 into the blue light beam BLc2 as counterclockwise circularlypolarized light. The blue light beam BLc2 emitted from the diffusiondevice 26 passes the first light collection element 25 toward the +Zdirection, and then enters the first retardation element 24 once again.On this occasion, the blue light beam BLc2 which enters the firstretardation element 24 from the first light collection element 25 isconverted by the first retardation element 24 into the blue light beamBLp as the P-polarized light. The blue light beam BLp as the P-polarizedlight is transmitted through the first polarization split element 51toward the +Z direction, transmitted through the second optical elementtoward the +Z direction, and then enters the first color separationelement 29.

Configuration of Second Light Collection Element

The second light collection element 27 is disposed at the −Z directionside of the first optical element 52. Specifically, the second lightcollection element 27 is disposed between the first optical element 52and the wavelength conversion element 28 on the Z axis. The second lightcollection element 27 converges the blue light beam BLs as theS-polarized light reflected by the first optical element 52 on thewavelength conversion element 28. Further, the second light collectionelement 27 collimates the yellow light beam YL which is emitted from thewavelength conversion element 28 and is described later, and then emitsthe result toward the first optical element 52. In the example shown inFIG. 3, the second light collection element 27 is constituted by twoconvex lenses, namely a first lens 271 and a second lens 272. It shouldbe noted that the number of the lenses constituting the second lightcollection element 27 is not particularly limited.

Configuration of Wavelength Conversion Element

The wavelength conversion element 28 is disposed at the −Z directionside of the second light collection element 27. In other words, thewavelength conversion element 28 is disposed at the −Z direction side ofthe first optical element 52. The wavelength conversion element 28 is areflective wavelength conversion element which is excited by the lightentering the wavelength conversion element, and emits light having adifferent wavelength band from the wavelength band of the light havingentered the wavelength conversion element 28 toward an oppositedirection to the incident direction of the light. In other words, thewavelength conversion element 28 performs the wavelength conversion onthe light which enters the wavelength conversion element 28, and thenemits the light on which the wavelength conversion has been performedtoward the opposite direction to the incident direction of the light.

In the present embodiment, the wavelength conversion element 28 includesa yellow phosphor which is excited by blue light and emits yellow light.Specifically, the wavelength conversion element 28 includes, forexample, an yttrium aluminum garnet (YAG) type phosphor containingcerium (Ce) as an activator. The wavelength conversion element 28 emitsfluorescence having a wavelength band longer than the blue wavelengthband of the blue light beam BLs entering the wavelength conversionelement 28 along the −Z direction, namely the yellow light beam YL asunpolarized light, toward the +Z direction. The yellow light beam YL hasa wavelength band of, for example, 500 through 650 nm. The yellow lightbeam YL is light having a wavelength band including the green wavelengthband and the red wavelength band. Therefore, the wavelength conversionelement 28 performs the wavelength conversion on the blue light beam BLsas the S-polarized light which enters the wavelength conversion element28 along the −Z direction from the first optical element 52, and emitsthe yellow light beam YL having a wavelength band including the greenwavelength band and the red wavelength band different from the bluewavelength band toward the +Z direction as an opposite direction to the−Z direction.

The yellow light beam YL having the wavelength band including the greenwavelength band and the red wavelength band in the present embodiment,namely the yellow light beam YL as the unpolarized light, corresponds toa second light beam having a second wavelength band in the appendedclaims.

The yellow light beam YL emitted from the wavelength conversion element28 is transmitted through the second light collection element 27 alongthe +Z direction to thereby be collimated, and then enters the firstoptical element 52. Since the first optical element 52 has acharacteristic of transmitting the light in the wavelength bandincluding the green wavelength band and the red wavelength band, theyellow light beam YL is transmitted through the first optical element 52along the +Z direction to enter the second polarization split element23.

It should be noted that the wavelength conversion element 28 in thepresent embodiment is a stationary wavelength conversion element, butinstead of this configuration, it is possible to use a rotary wavelengthconversion element provided with a rotation device for rotating thewavelength conversion element 28 centering on a rotational axis parallelto the Z axis. When using the rotary wavelength conversion element, arise in temperature of the wavelength conversion element 28 issuppressed, and thus, it is possible to increase the wavelengthconversion efficiency.

As described above, the polarization split layer 231 of the secondpolarization split element 23 has a polarization split characteristic ofreflecting the S-polarized light and transmitting the P-polarized lightwith respect to the light in the wavelength band including the greenwavelength band and the red wavelength band. Therefore, out of theyellow light beam YL as the unpolarized light having entered the secondpolarization split element 23, the yellow light beam YLs as theS-polarized light is reflected by the polarization split layer 231toward the −X direction, and then enters the second optical element 22.The yellow light beam YLs as the S-polarized light having entered thesecond optical element 22 is reflected by the second optical element 22toward the +Z direction to enter the first color separation element 29.

Meanwhile, out of the yellow light beam YL as the unpolarized lighthaving entered the second polarization split element 23, the yellowlight beam YLp as the P-polarized light is transmitted through thepolarization split layer 231 toward the +Z direction to be emitted fromthe second polarization split element 23, and then enters the secondcolor separation element 33 via the fourth retardation element 32.

It should be noted that the yellow light beam YLp as the P-polarizedlight in the present embodiment corresponds to the second light beampolarized in the first polarization direction in the appended claims.The yellow light beam YLs as the S-polarized light corresponds to thesecond light beam polarized in the second polarization direction in theappended claims.

Configuration of First Color Separation Element

FIG. 4 is a side view of the light source device 2 viewed from the −Xdirection. In other words, FIG. 4 shows the state of the first colorseparation element 29 viewed from the −X direction. In FIG. 4, in orderto make the drawing eye-friendly, there is omitted the illustration ofthe light source section 21, the first polarization split element 51,the first optical element 52, the first light collection element 25, thediffusion device 26, the second light collection element 27, thewavelength conversion element 28, and so on out of the constituentsshown in FIG. 3.

As shown in FIG. 4, the first color separation element 29 is disposed atthe +Z direction side of the second optical element 22. The first colorseparation element 29 has a dichroic prism 291 and a reflecting prism292. The dichroic prism 291 and the reflecting prism 292 are arrangedside by side along the Y axis. The first color separation element 29separates light emitted toward the +Z direction from the second opticalelement 22 into the blue light beam BLp having the blue wavelength bandand the yellow light beam YLs having the yellow wavelength band.

The blue light beam BLp having the blue wavelength band in the presentembodiment corresponds to a third light beam having the first wavelengthband in the appended claims. The yellow light beam YLs having the yellowwavelength band in the present embodiment corresponds to a fourth lightbeam having the second wavelength band in the appended claims.

The light including the blue light beam BLp and the yellow light beamYLs emitted from the second optical element 22 enters the dichroic prism291. The dichroic prism 291 is formed of a prism type color separationelement formed by combining two base members each having a substantiallyisosceles right triangular prismatic shape with each other to form asubstantially rectangular solid shape. On the interface between the twobase members, there is disposed a color separation layer 2911. The colorseparation layer 2911 is tilted 45° with respect to the Y axis and the Zaxis. In other words, the color separation layer 2911 is tilted 45° withrespect to the X-Y plane and the X-Z plane.

The color separation layer 2911 functions as a dichroic mirror whichreflects the blue light and transmits colored light having a longerwavelength band than the blue wavelength band, namely the yellow light,out of the light which enters the color separation layer 2911.Therefore, the yellow light beam YLs out of the light having entered thedichroic prism 291 along the +Z direction from the second opticalelement 22 is transmitted through the color separation layer 2911 towardthe +Z direction to be emitted outside the dichroic prism 291.

In contrast, the blue light beam BLp out of the light having entered thedichroic prism 291 along the +Z direction from the second opticalelement 22 is reflected toward the −Y direction by the color separationlayer 2911. It should be noted that it is possible to adopt a dichroicmirror having the color separation layer 2911 instead of the dichroicprism 291.

The reflecting prism 292 is disposed at the −Y direction side of thedichroic prism 291. The blue light beam BLp reflected by the colorseparation layer 2911 enters the reflecting prism 292. The reflectingprism 292 is a prism type reflecting element formed by combining twobase members each having a substantially isosceles right triangularprismatic shape with each other to forma substantially rectangular solidshape. On the interface between the two base members, there is disposeda reflecting layer 2921. The reflecting layer 2921 is tilted 45° withrespect to the +Y direction and the +Z direction. In other words, thereflecting layer 2921 is tilted 45° with respect to the X-Y plane andthe X-Z plane. In other words, the reflecting layer 2921 is disposed inparallel to the color separation layer 2911.

The blue light beam BLp which enters the reflecting layer 2921 along the−Y direction from the dichroic prism 291 is reflected toward the +Zdirection by the reflecting layer 2921. The blue light beam BLpreflected by the reflecting layer 2921 is emitted from the reflectingprism 292 toward the +Z direction. It should be noted that it ispossible to adopt a reflecting mirror having the reflecting layer 2921instead of the reflecting prism 292.

Configuration of Reflecting Element

The reflecting element 31 is disposed at the +Z direction side of thedichroic prism 291. In other words, the reflecting element 31 isdisposed on the light path of the yellow light beam YLs emitted from thedichroic prism 291. The reflecting element 31 is formed of a half mirrorfor transmitting a part of the light which enters the reflecting element31, and reflecting the rest of the light. It is sufficient for thetransmittance and the reflectance of the half mirror to arbitrarily beset in accordance with the white balance of the light L to be emittedfrom the light source device 2, and for example, the transmittance isset to 80%, and the reflectance is set to 20%.

Therefore, a part of the yellow light beam YLs which has entered thereflecting element 31 is transmitted through the reflecting element 31,and is then emitted toward the homogenization device 4 shown in FIG. 1.In contrast, another part of the yellow light beam YLs which has enteredthe reflecting element 31 is reflected by the reflecting element 31 toreenter the dichroic prism 291. The another part of the yellow lightbeam YLs having entered the dichroic prism 291 is transmitted throughthe color separation layer 2911 toward the −Z direction, and returns tothe wavelength conversion element 28 via the second optical element 22,the second polarization split element 23, the first optical element 52,and the second light collection element 27.

The yellow phosphor included in the wavelength conversion element 28hardly absorbs the yellow light having entered the wavelength conversionelement 28 from the outside. Therefore, the yellow light beam YLs havingreturned to the wavelength conversion element 28 is repeatedly reflectedor diffused to thereby turn to the yellow light beam YL as theunpolarized light without being absorbed in the wavelength conversionelement 28. The yellow light beam YL as the unpolarized light is emittedonce again to the outside of the wavelength conversion element 28together with the yellow light beam YL newly generated in the yellowphosphor. The yellow light beam YL having been emitted from thewavelength conversion element 28 reenters the first optical element 52via the second light collection element 27 as described above. Asdescribed above, the ratio between the light intensity of the yellowlight beam YLs transmitted through the reflecting element 31 and thelight intensity of the yellow light beam YLs reflected by the reflectingelement 31 can be set in advance. Further, the reflecting element 31 canbe disposed so as to have contact with a surface from which the yellowlight beam YLs is emitted of the dichroic prism 291.

Configuration of Fifth Retardation Element

The fifth retardation element 30 is disposed at the +Z direction side ofthe reflecting prism 292. In other words, the fifth retardation element30 is disposed on the light path of the blue light beam BLp emitted fromthe reflecting prism 292. The fifth retardation element 30 is formed ofa ½ wave plate with respect to the blue wavelength band which the bluelight beam BLp has. The fifth retardation element 30 converts the bluelight beam BLp as the P-polarized light emitted from the reflectingprism 292 into the blue light beam BLs as the S-polarized light. Theblue light beam BLs obtained by the conversion into the S-polarizedlight by the fifth retardation element 30 is emitted toward the +Zdirection from the light source device 2, and then enters thehomogenization device 4 shown in FIG. 1. In other words, the blue lightbeam BLs is spatially separated from the yellow light beam YLs, and isemitted from an exit position different from the exit position of theyellow light beam YLs in the light source device 2, and then enters thehomogenization device 4. In particular, the blue light beam BLs isemitted from the exit position distant toward the −Y direction from theexit position of the yellow light beam YLs in the light source device 2,and then enters the homogenization device 4.

Configuration of Fourth Retardation Element

FIG. 5 is a side view of the light source device 2 viewed from the +Xdirection. In other words, FIG. 5 shows the state of the second colorseparation element 33 viewed from the +X direction. In FIG. 5, in orderto make the drawing eye-friendly, there is omitted the illustration ofthe light source section 21, the first polarization split element 51,the first optical element 52, the first light collection element 25, thediffusion device 26, the second light collection element 27, thewavelength conversion element 28, and so on out of the constituentsshown in FIG. 3.

As shown in FIG. 3 and FIG. 5, the fourth retardation element 32 isdisposed at the +Z direction side of the second polarization splitelement 23. The yellow light beam YLp having been transmitted throughthe second polarization split element 23 enters the fourth retardationelement 32. The fourth retardation element 32 is formed of a ½ waveplate with respect to the wavelength band which the yellow light beamYLp has. The fourth retardation element 32 converts the yellow lightbeam YLp as the P-polarized light into the yellow light beam YLs as theS-polarized light. The yellow light beam YLs obtained by the conversioninto the S-polarized light enters the second color separation element33.

Configuration of Second Color Separation Element

As shown in FIG. 5, the second color separation element 33 is disposedat the +Z direction side of the second polarization split element 23.The second color separation element 33 has a dichroic prism 331 and areflecting prism 332. The dichroic prism 331 and the reflecting prism332 are arranged side by side along the Y axis. The second colorseparation element 33 separates the yellow light beam YLs as theS-polarized light emitted toward the +Z direction from the secondpolarization split element 23 via the fourth retardation element 32 intothe green light beam GLs in the green wavelength band different from thewavelength band of the yellow light beam YLs and the red light beam RLsin the red wavelength band different from the wavelength band of theyellow light beam YLs and the green wavelength band.

The green light beam GLs in the green wavelength band in the presentembodiment corresponds to a fifth light beam having a third wavelengthband. The red light beam RLs in the red wavelength band in the presentembodiment corresponds to a sixth light beam having a fourth wavelengthband.

The dichroic prism 331 is formed of a prism type color separationelement similarly to the dichroic prism 291. On the interface betweenthe two base members, there is disposed a color separation layer 3311.The color separation layer 3311 is tilted 45° with respect to the +Ydirection and the +Z direction. In other words, the color separationlayer 3311 is tilted 45° with respect to the X-Y plane and the X-Zplane. The color separation layer 3311 is disposed in parallel to thereflecting layer 3321.

The color separation layer 3311 functions as a dichroic mirror whichtransmits the red light component and reflects the green light componentout of the light entering the color separation layer 3311. Therefore,the red light beam RLs as the S-polarized light out of the yellow lightbeam YLs having entered the dichroic prism 331 is transmitted toward the+Z direction through the color separation layer 3311 to be emittedoutside the dichroic prism 331. The red light beam RLs as theS-polarized light is emitted toward the +Z direction from the lightsource device 2, and then enters the homogenization device 4. In otherwords, the red light beam RLs is spatially separated from the yellowlight beam YLs and the blue light beam BLs, and is emitted from aposition different from those of the yellow light beam YLs and the bluelight beam BLs, and then enters the homogenization device 4. In otherwords, the red light beam RLs is emitted from the exit position distanttoward the +X direction from the exit position of the yellow light beamYLs in the light source device 2, and then enters the homogenizationdevice 4.

In contrast, the green light beam GLs as the S-polarized light out ofthe yellow light beam YLs having entered the dichroic prism 331 isreflected toward the −Y direction by the color separation layer 3311. Itshould be noted that it is possible to use a dichroic mirror having thecolor separation layer 3311 instead of the dichroic prism 331.

The reflecting prism 332 has substantially the same configuration as thereflecting prism 292. Specifically, the reflecting prism 332 has areflecting layer 3321 which is parallel to the color separation layer2911, the color separation layer 3311, and the reflecting layer 2921.

The green light beam GLs which is reflected by the color separationlayer 3311, and then enters the reflecting layer 3321 is reflected bythe reflecting layer 3321 toward the +Z direction. The green light beamGLs having been reflected by the reflecting layer 3321 is emittedoutside the reflecting prism 332. The green light beam GLs is emittedtoward the +Z direction from the light source device 2, and then entersthe homogenization device 4. Specifically, the green light beam GLs isspatially separated from the yellow light beam YLs, the blue light beamBLs, and the red light beam RLs, and is emitted from a positiondifferent from those of the yellow light beam YLs, the blue light beamBLs, and the red light beam RLs, and then enters the homogenizationdevice 4. In other words, the green light beam GLs is emitted from theexit position which is distant toward the −Y direction from the exitposition of the red light beam RLs in the light source device 2, and isdistant toward the +X direction from the exit position of the blue lightbeam BLs, and then enters the homogenization device 4.

Configuration of Homogenization Device

As shown in FIG. 1, the homogenization device 4 homogenizes theilluminance in the image formation area of the light modulation device 6irradiated with the light beams emitted from the light source device 2.The homogenization device 4 has a first multi-lens 41, a secondmulti-lens 42, and a superimposing lens 43.

The first multi-lens 41 has a plurality of lenses 411 arranged in amatrix in a plane perpendicular to a central axis of the light Lentering the first multi-lens 41 from the light source device 2, namelythe illumination light axis Ax. The first multi-lens 41 divides thelight entering the first multi-lens 41 from the light source device 2into a plurality of partial light beams with the plurality of lenses411.

FIG. 6 is a schematic diagram showing positions of incidence of therespective colored light beams in the first multi-lens 41 viewed fromthe −Z direction.

As shown in FIG. 6, the yellow light beam YLs, the blue light beam BLs,the red light beam RLs, and the green light beam GLs emitted from thelight source device 2 enter the first multi-lens 41. The yellow lightbeam YLs emitted from the position at the −X direction side and at the+Y direction side in the light source device 2 enters a plurality oflenses 411 included in an area A1 located at the −X direction side andat the +Y direction side in the first multi-lens 41. Further, the bluelight beam BLs emitted from the position at the −X direction side and atthe −Y direction side in the light source device 2 enters a plurality oflenses 411 included in an area A2 located at the −X direction side andat the −Y direction side in the first multi-lens 41.

The red light beam RLs emitted from the position at the +X directionside and at the +Y direction side in the light source device 2 enters aplurality of lenses 411 included in an area A3 located at the +Xdirection side and at the +Y direction side in the first multi-lens 41.Further, the green light beam GLs emitted from the position at the +Xdirection side and at the −Y direction side in the light source device 2enters a plurality of lenses 411 included in an area A4 located at the+X direction side and at the −Y direction side in the first multi-lens41. Each of the colored light beams having entered the lenses 411 isconverted into a plurality of partial light beams, and enters lenses 421corresponding respectively to the lenses 411 in the second multi-lens42.

The blue light beam BLs out of the light beam L emitted from the lightsource device 2 according to the present embodiment corresponds to thethird light beam in the appended claims. The yellow light beam YLscorresponds to the fourth light beam in the appended claims. The greenlight beam GLs corresponds to the fifth light beam in the appendedclaims. The red light beam RLs corresponds to the sixth light beam inthe appended claims.

As shown in FIG. 1, the second multi-lens 42 has the plurality of lenses421 which is arranged in a matrix in a plane perpendicular to theillumination light axis Ax, and at the same time, correspondsrespectively to the plurality of lenses 411 of the first multi-lens 41.The partial light beams emitted from the lenses 411 opposed respectivelyto the lenses 421 enter the respective lenses 421. Each of the lenses421 makes the partial light beam enter the superimposing lens 43.

The superimposing lens 43 superimposes the plurality of partial lightbeams entering the superimposing lens 43 from the second multi-lens 42on each other in the image formation area of the light modulation device6. In particular, the second multi-lens 42 and the superimposing lens 43make the yellow light beam YLs, the blue light beam BLs, the red lightbeam RLs, and the green light beam GLs each divided into the pluralityof partial light beams enter a plurality of microlenses 621 constitutinga microlens array 62 described later of the light modulation device 6 atrespective angles different from each other via the field lens 5.

Configuration of Light Modulation Device

As shown in FIG. 1, the light modulation device 6 modulates the lightemitted from the light source device 2. In particular, the lightmodulation device 6 modulates each of the colored light beams which areemitted from the light source device 2, and then enter the lightmodulation device 6 via the homogenization device 4 and the field lens 5in accordance with image information to form the image lightcorresponding to the image information. The light modulation device 6 isprovided with the single liquid crystal panel 61 and a single microlensarray 62.

Configuration of Liquid Crystal Panel

FIG. 7 is a schematic enlarged view of a part of the light modulationdevice 6 viewed from the −Z direction. In other words, FIG. 7 shows acorrespondence relationship between the pixels PX provided to the liquidcrystal panel 61 and the microlenses 621 provided to the microlens array62.

As shown in FIG. 7, the liquid crystal panel 61 has the plurality ofpixels PX arranged in a matrix in a plane perpendicular to theillumination light axis Ax (the Z axis).

One pixel PX has a plurality of sub-pixels SX for respectivelymodulating colored light beams different in color from each other. Inthe present embodiment, each of the pixels PX has four sub-pixels SX(SX1 through SX4). Specifically, in one pixel PX, the first sub-pixelSX1 is disposed at a position at the −X direction side and at the +Ydirection side. The second sub-pixel SX2 is disposed at a position atthe −X direction side and at the −Y direction side. The third sub-pixelSX3 is disposed at a position at the +X direction side and at the +Ydirection side. The fourth sub-pixel SX4 is disposed at a position atthe +X direction side and at the −Y direction side.

Configuration of Microlens Array

As shown in FIG. 1, the microlens array 62 is disposed at the −Zdirection side as the side of incidence of light with respect to theliquid crystal panel 61. The microlens array 62 guides the plurality ofcolored light beams entering the microlens array 62 to the individualpixels PX. The microlens array 62 has the plurality of microlenses 621corresponding to the plurality of pixels PX.

As shown in FIG. 7, the plurality of microlenses 621 is arranged in amatrix in a plane perpendicular to the illumination light axis Ax. Inother words, the plurality of microlenses 621 is arranged in a matrix inan orthogonal plane with respect to the central axis of the lightentering the plurality of microlenses 621 from the field lens 5. In thepresent embodiment, one microlens 621 is disposed so as to correspond tothe two sub-pixels arranged in the +X direction and the two sub-pixelsarranged in the +Y direction. In other words, one microlens 621 isdisposed so as to correspond to the four sub-pixels SX1 through SX4arranged 2×2 in the X-Y plane.

The yellow light beam YLs, the blue light beam BLs, the red light beamRLs, and the green light beam GLs superimposed by the homogenizationdevice 4 enter the microlenses 621 at respective angles different fromeach other. The microlenses 621 make the colored light beams enteringthe microlens 621 enter the sub-pixels SX corresponding to the coloredlight beams. Specifically, out of the sub-pixels SX of the pixel PXcorresponding to the microlens 621, the microlens 621 makes the yellowlight beam YLs enter the first sub-pixel SX1, makes the blue light beamBLs enter the second sub-pixel SX2, makes the red light beam RLs enterthe third sub-pixel SX3, and makes the green light beam GLs enter thefourth sub-pixel SX4. Thus, the colored light beams correspondingrespectively to the sub-pixels SX1 through SX4 enter the respectivesub-pixels SX1 through SX4, and the colored light beams are respectivelymodulated by the corresponding sub-pixels SX1 through SX4. In such amanner, the image light modulated by the liquid crystal panel 61 isprojected by the projection optical device 7 on the projection targetsurface such as a screen not shown.

Advantages of First Embodiment

In the related-art projector described in Document 1, the lamp is usedas the light source. Since the light emitted from the lamp is notuniform in polarization direction, in order to use the liquid crystalpanel as the light modulation device, a polarization conversion devicefor uniforming the polarization direction becomes necessary. For theprojector, there is generally used the polarization conversion deviceprovided with a multi-lens array and a polarization split element (PBS)array. However, in order to reduce the size of the projector, there arerequired the multi-lens array and the PBS array narrow in pitch, but itis extremely difficult to manufacture the PBS array narrow in pitch.

To cope with this problem, the light source device 2 according to thepresent embodiment is provided with the light source section 21 whichemits the blue light beams BLp, BLs having the blue wavelength band andrespectively including the P-polarized light and the S-polarized light,the first polarization split element 51 which transmits the blue lightbeam BLp entering the first polarization split element 51 along the +Xdirection from the light source section 21 toward the +X direction, andreflects the blue light beam BLs toward the −Z direction crossing the +Xdirection, the first optical element 52 which is disposed at the +Xdirection side of the first polarization split element 51, and reflectsthe blue light beam BLs entering the first optical element 52 along the+X direction from the first polarization split element 51 toward the −Zdirection, the diffusion plate 261 which is disposed at the −Z directionside of the first polarization split element 51, diffuses the blue lightbeam BLc1 entering the diffusion plate 261 along the −Z direction fromthe first polarization split element 51, and emits the blue light beamBLc2 thus diffused toward the +Z direction as the opposite direction tothe −Z direction, the wavelength conversion element 28 which is disposedat the −Z direction side of the first optical element 52, and performsthe wavelength conversion on the blue light beam BLs entering thewavelength conversion element 28 along the −Z direction from the firstoptical element 52 to emit the yellow light beam YL having thewavelength band including the green wavelength band and the redwavelength band different from the blue wavelength band toward the +Zdirection, the second polarization split element 23 which is disposed atthe +Z direction side of the first optical element 52, which the yellowlight beam YL enters along the +Z direction from the first opticalelement 52, and which transmits the yellow light beam YLp as theP-polarized light toward the +Z direction, and reflects the yellow lightbeam YLs as the S-polarized light toward the −X direction as theopposite direction to the +X direction, and the second optical element22 which is disposed at the −X direction side of the second polarizationsplit element 23, and reflects the yellow light beam YLs as theS-polarized light entering the second optical element 22 along the −Xdirection from the second polarization split element 23 toward the +Zdirection, wherein the blue light beam BLp which enters the firstpolarization split element 51 along the +Z direction from the diffusionplate 261 is transmitted by the first polarization split element 51toward the +Z direction, the yellow light beam YL which enters the firstoptical element 52 along the +Z direction from the wavelength conversionelement 28 is transmitted by the first optical element 52 toward the +Zdirection, and the blue light beam BLp which enters the second opticalelement 22 along the +Z direction from the first polarization splitelement 51 is transmitted by the second optical element 22 toward the +Zdirection.

In the present embodiment, the four colors of colored light beamsuniform in the polarization direction, namely the blue light beam BLs asthe S-polarized light, the yellow light beam YLs as the S-polarizedlight, the green light beam GLs as the S-polarized light, and the redlight beam RLs as the S-polarized light, are emitted from the lightsource device 2. According to this configuration, it is possible torealize the light source device 2 capable of emitting the plurality ofcolored light beams spatially separated from each other and uniformed inthe polarization direction without using the polarization conversionelement narrow in pitch described above. Thus, it is possible to reducethe light source device 2 in size, and by extension, it is possible toachieve reduction in size of the projector 1.

Further, in the projector 1 according to the present embodiment, sincethe yellow light beam YLs enters the light modulation device 6 inaddition to the blue light beam BLs, the green light beam GLs, and thered light beam RLs, it is possible to increase the luminance of theimage projected from the projection optical device 7.

When considering the light source device with which substantially thesame advantages as described above can be obtained, it is conceivable toadopt a configuration in which, for example, two polarization splitelements consisting of the first polarization split element and thesecond polarization split element are arranged in sequence in the +Xdirection, the diffusion element is disposed at the −Z direction side ofthe first polarization split element, the wavelength conversion elementis disposed at the −Z direction side of the second polarization splitelement, and the four colored light beams obtained from the diffusionelement and the wavelength conversion element are emitted toward the +Zdirection on the condition that substantially the same light sourcesection as in the present embodiment is used. This light source devicewill hereinafter be referred to as a light source device according to acomparative example.

In the light source device according to the comparative example, it isnecessary to make the blue light beam BLs as the S-polarized lightreflected toward the −Z direction by the first polarization splitelement enter the diffusion element, and to make the second polarizationsplit element reflect the blue light beam BLp as the P-polarized lighttransmitted toward the +X direction through the first polarization splitelement toward the −Z direction to enter the wavelength conversionelement. In other words, it is necessary to transmit the blue light beamBLp as the P-polarized light in the first polarization split element onthe one hand, but it is necessary to reflect the blue light beam BLp asthe P-polarized light in the second polarization split element.

However, it is common for the polarization split film used in thepolarization split element to have a characteristic of reflecting theS-polarized light and transmitting the P-polarized light. Therefore,when realizing the light source device according to the comparativeexample, it is difficult to manufacture the second polarization splitelement for reflecting the blue light as the P-polarized light.Specifically, in order to realize the characteristic described above, itis necessary to make the number of layers in the dielectric multilayerfilm which forms the polarization split film of the second polarizationsplit element extremely large, and it is difficult to form thedielectric multilayer film. Further, since the dielectric multilayerfilm extremely large in the number of layers is high in absorption oflight, there is a problem that a loss of light occurs. Further, since itis necessary for the polarization split film of the second polarizationsplit element to have a polarization split characteristic of reflectingthe yellow light as the S-polarized light and transmitting the yellowlight as the P-polarized light with respect to the yellow light, it ismore difficult to manufacture the polarization split film of reflectingthe P-polarized light with respect to the blue light while keeping thepolarization split characteristic with respect to the yellow light.

To cope with this problem, in the light source device 2 according to thepresent embodiment, only the blue light beams BLp, BLs enter the firstpolarization split element 51, and it is sufficient for the firstpolarization split element 51 to have the polarization splitcharacteristic of transmitting the P-polarized light and reflecting theS-polarized light with respect to the blue light beams BLp, BLs. It issufficient for the first optical element 52 to have a characteristic ofreflecting the blue light beam BLs as the S-polarized light andtransmitting the yellow light beam YL. Only the yellow light beam YLenter the second polarization split element 23, and it is sufficient forthe second polarization split element to have the polarization splitcharacteristic of transmitting the P-polarized light and reflecting theS-polarized light with respect to the yellow light. It is sufficient forthe second optical element 22 to have a characteristic of transmittingthe blue light beam BLp as the P-polarized light and reflecting theyellow light beam YLs as the S-polarized light.

As described above, in the light source device 2 according to thepresent embodiment, the dielectric multilayer film for forming each ofthe first polarization split element 51, the first optical element 52,the second polarization split element 23, and the second optical element22 is not required to have a special polarization split characteristicsuch as a characteristic of reflecting the P-polarized light andtransmitting the S-polarized light. Therefore, it is easy to form thedielectric multilayer film. Specifically, since it is possible to reducethe number of layers of the dielectric multilayer film, it is possibleto achieve reduction of the manufacturing cost and an improvement of theyield ratio. Further, it is possible to manufacture the firstpolarization split element 51, the first optical element 52, the secondpolarization split element 23, and the second optical element allexcellent in light separation characteristic. As described above,according to the light source device 2 related to the presentembodiment, it is possible to solve the problem described above whichthe light source device according to the comparative example has.

Further, the light source device 2 according to the present embodimentis further provided with the first retardation element 24 which isdisposed between the first polarization split element 51 and thediffusion plate 261, and which the blue light beam BLs as theS-polarized light enters along the −Z direction from the firstpolarization split element 51.

According to this configuration, it is possible to convert the bluelight beam BLc2 as the circularly polarized light having been emittedfrom the diffusion plate 261 with the first retardation element 24 intothe blue light beam BLp as the P-polarized light, and make the result betransmitted through the first polarization split element 51 to enter thesecond optical element 22. Thus, it is possible to increase the useefficiency of the blue light beam BLc2 emitted from the diffusion plate261.

Further, in the light source device 2 according to the presentembodiment, the light source section 21 has the light emitting elements211 for emitting the blue light beams BLs having the blue wavelengthband, and the second retardation element 2131 which the blue light beamsBLs emitted from the light emitting elements 211 enter, and which emitsthe blue light including the blue light beam BLs as the S-polarizedlight and the blue light beam BLp as the P-polarized light.

According to this configuration, it is possible to surely make the bluelight beam BLp as the P-polarized light and the blue light beam BLs asthe S-polarized light enter the first polarization split element 51.Further, according to this configuration, since the polarizationdirections of the light beams emitted from the plurality of lightemitting elements 211 are allowed to be the same, it is sufficient todispose the same solid-state light sources in the same orientation, andthus, it is possible to simplify the configuration of the light sourcesection 21.

Further, in the light source device 2 according to the presentembodiment, there is adopted the configuration in which the secondretardation element 2131 can rotate centering on the rotational axisextending along the proceeding direction of the blue light beam BLsentering the second retardation element 2131.

According to this configuration, by adjusting the rotational angle ofthe second retardation element 2131, it is possible to adjust the ratiobetween the light intensity of the blue light beam BLs which enters thefirst polarization split element 51 and the light intensity of the bluelight beam BLp which enters the first polarization split element 51.Thus, it is possible to adjust the light intensity ratio between theblue light beam BLs, and the yellow light beam YLs, the green light beamGLs, and the red light beam RLs emitted from the light source device 2,and therefore, it is possible to adjust the white balance of the lightsource device 2.

Further, in the light source device 2 according to the presentembodiment, there is disposed the fourth retardation element 32 betweenthe second polarization split element 23 and the second color separationelement 33.

According to this configuration, it is possible to convert the yellowlight beam YLp as the P-polarized light emitted from the secondpolarization split element 23 into the yellow light beam YLs as theS-polarized light with the fourth retardation element 32. Thus, it ispossible to convert the green light beam GLs and the red light beam RLsemitted from the second color separation element 33 into the light asthe S-polarized light, and it is possible to uniform all of the bluelight beam BLs, the yellow light beam YLs, the green light beam GLs, andthe red light beam RLs emitted from the light source device 2 into thelight as the S-polarization component.

Further, in the light source device 2 according to the presentembodiment, there is disposed the fifth retardation element 30 formed ofthe ½ wave plate with respect to the blue wavelength band at the +Zdirection side of the reflecting prism 292.

According to this configuration, it is possible to convert the bluelight beam BLp as the P-polarized light emitted from the reflectingprism 292 into the blue light beam BLs as the S-polarized light with thefifth retardation element 30. Thus, it is possible to uniform all of theblue light beam BLs, the yellow light beam YLs, the green light beamGLs, and the red light beam RLs emitted from the light source device 2into the S-polarized light.

Further, in the light source device 2 according to the presentembodiment, the reflecting element 31 for reflecting a part of theyellow light beam YLs is disposed at the light exit side of the yellowlight beam YLs in the first color separation element 29.

According to this configuration, by using the reflecting elements 31different in reflectance from each other, it is possible to adjust theratio in light intensity between the yellow light beam YLs, and thegreen light beam GLs and the red light beam RLs emitted from the lightsource device 2. Thus, it is possible to adjust the white balance of thelight source device 2. Further, by increasing the ratio of the lightintensity of the yellow light beam YLs to the light intensity of othercolored light beams, it is possible to increase the luminance of theprojection image. Further, by increasing the ratio of the lightintensity of the green light beam GLs and the red light beam RLs to thelight intensity of other colored light beams, it is possible to increasethe color reproducibility of the projection image.

Further, the light source device 2 according to the present embodimentis provided with the first light collection element 25 for collectingthe blue light beam BLc1 toward the diffusion plate 261.

According to this configuration, it is possible to efficiently convergethe blue light beam BLc1 emitted from the first retardation element 24on the diffusion plate 261 with the first light collection element 25,and at the same time, it is possible to collimate the blue light beamBLc2 emitted from the diffusion plate 261. Thus, it is possible tosuppress the loss of the blue light beam BLs, and therefore, it ispossible to increase the use efficiency of the blue light beam BLs.

Further, the light source device 2 according to the present embodimentis provided with the second light collection element 27 for collectingthe blue light beam BLs toward the wavelength conversion element 28.

According to this configuration, it is possible to efficiently convergethe blue light beam BLs emitted from the first optical element 52 on thewavelength conversion element 28 with the second light collectionelement 27, and at the same time, it is possible to collimate the yellowlight beam YL emitted from the wavelength conversion element 28. Thus,it is possible to suppress the loss of the blue light beam BLp and theyellow light beam YL, and therefore, it is possible to increase the useefficiency of the blue light beam BLp and the yellow light beam YL.

The projector 1 according to the present embodiment is provided with thelight source device 2 according to the present embodiment, the lightmodulation device 6 for modulating the light emitted from the lightsource device 2 in accordance with the image information, and theprojection optical device 7 for projecting the light modulated by thelight modulation device 6.

According to this configuration, it is possible to realize the projector1 of a single plate type small in size and excellent in light useefficiency.

Further, the projector 1 according to the present embodiment is providedwith the homogenization device 4 located between the light source device2 and the light modulation device 6.

According to this configuration, it is possible to substantiallyuniformly illuminate the light modulation device 6 with the blue lightbeam BLs, the yellow light beam YLs, the green light beam GLs, and thered light beam RLs emitted from the light source device 2. Thus, it ispossible to suppress the color unevenness and the luminance unevennessin the projection image.

Further, in the projector 1 according to the present embodiment, thelight modulation device 6 is provided with the microlens array 62 havingthe plurality of microlenses 621 corresponding to the plurality ofpixels PX.

According to this configuration, it is possible to make the four coloredlight beams entering the light modulation device 6 enter thecorresponding four sub-pixels SX in the liquid crystal panel 61 with themicrolens 621. Thus, it is possible to make the colored light beamsemitted from the light source device 2 efficiently enter the respectivesub-pixels SX, and thus, it is possible to increase the use efficiencyof the colored light beams.

Second Embodiment

A second embodiment of the present disclosure will hereinafter bedescribed using FIG. 8 and FIG. 9.

A light source device according to the second embodiment issubstantially the same in basic configuration as that of the firstembodiment, but is different in configuration of the reflecting elementfrom that of the first embodiment. Therefore, the overall description ofthe light source device will be omitted.

FIG. 8 is a side view of a light source device 12 according to thesecond embodiment viewed from the −X direction. FIG. 9 is a schematicdiagram showing positions of incidence of colored light beams on amulti-lens. It should be noted that in FIG. 8, in order to make thedrawing eye-friendly, there is omitted the illustration of the lightsource section 21, the first polarization split element 51, the firstoptical element 52, the first light collection element 25, the diffusiondevice 26, the second light collection element 27, the wavelengthconversion element 28, and so on out of the constituents shown in FIG.3.

In FIG. 8 and FIG. 9, the constituents common to the drawings used inthe first embodiment are denoted by the same reference symbols, and thedescription thereof will be omitted.

As shown in FIG. 8, the light source device 12 according to the presentembodiment is provided with a third color separation element 35 insteadof the reflecting element in the light source device 2 according to thefirst embodiment. Specifically, the third color separation element 35 isdisposed at the +Z direction side of the dichroic prism 291 on the lightpath of the yellow light beam YLs separated by the first colorseparation element 29. The third color separation element 35 is formedof a dichroic mirror having a characteristic of transmitting a greenlight beam GLs2 and reflecting the red light beam RLs. It should benoted that it is also possible to use a dichroic prism as the thirdcolor separation element 35 instead of the dichroic mirror.

Therefore, the green light beam GLs2 included in the yellow light beamYLs which enters the third color separation element 35 from the dichroicprism 291 of the first color separation element 29 is transmittedthrough the third color separation element 35 to be transmitted outsidethe light source device 12. In other words, the light source device 12emits the green light beam GLs2 instead of the yellow light beam YLsfrom the position where the yellow light beam YLs is emitted in thelight source device 2 according to the first embodiment.

In the present embodiment, the green light beam GLs2 emitted from theposition where the yellow light beam YLs is emitted in the firstembodiment corresponds to the fourth light beam in the appended claims.

In contrast, the red light beam RLs included in the yellow light beamYLs which enters the third color separation element 35 is reflected bythe third color separation element 35 to enter the dichroic prism 291from the −Z direction. Similarly to the yellow light beam YLs reflectedby the reflecting element 31 in the light source device 2 according tothe first embodiment, the red light beam RLs returns to the wavelengthconversion element 28 via the second optical element 22, the secondpolarization split element 23, the first optical element 52, and thesecond light collection element 27.

As described above, since the yellow phosphor included in the wavelengthconversion element 28 hardly absorbs the yellow light having entered thewavelength conversion element 28 from the outside, the yellow phosphorhardly absorbs the red light. Therefore, the red light beam RLs havingentered the wavelength conversion element 28 is repeatedly reflectedinside the wavelength conversion element 28 to thereby turn to a redlight beam as unpolarized light, and is then emitted outside thewavelength conversion element 28 together with the yellow light beam YLgenerated by the yellow phosphor. The red light beam RLs as theS-polarized light out of the red light beam emitted from the wavelengthconversion element 28 is transmitted through the first optical element52, then reflected by the second polarization split element 23, and thenenters the first color separation element 29 once again to repeat thebehavior described above. In contrast, the red light beam RLp as theP-polarized light out of the red light beam emitted from the wavelengthconversion element 28 is transmitted in sequence through the firstoptical element 52 and the second polarization split element 23, and isthen emitted outside the light source device 12 via the fourthretardation element 32 and the second color separation element 33.

As shown in FIG. 9, the light source device 12 emits the green lightbeam GLs2, the blue light beam BLs, the red light beam RLs, and thegreen light beam GLs. The green light beam GLs2 is emitted from theposition at the −X direction side and at the +Y direction side in thelight source device 2, and then enters a plurality of lenses 411disposed in the area A1 located at the −X direction side and at the +Ydirection side in the first multi-lens 41. Although not shown in thedrawings, the green light beam GLs2 enters the microlenses 621 via thefirst multi-lens 41, the second multi-lens 42, the superimposing lens43, and the field lens 5 similarly to the yellow light beam YLs in thefirst embodiment. The green light beam GLs2 having entered each of themicrolenses 621 enters the first sub-pixel SX1 of the pixel PXcorresponding to that microlens 621.

Advantages of Second Embodiment

Also in the present embodiment, it is possible to obtain substantiallythe same advantages as in the first embodiment such as the advantagethat it is possible to realize the light source device 12 capable ofemitting the plurality of colored light beams made uniform inpolarization direction without using the polarization conversion elementnarrow in pitch, the advantage that it is possible to achieve thereduction in size of the light source device 12 and the projector 1, andthe advantage that it is easy to form the dielectric multilayer film,and it is possible to manufacture the optical element and thepolarization split element which are low in cost, and excellent in lightseparation characteristic.

Further, in the light source device 12 according to the secondembodiment, since the green light beam GLs2 is emitted instead of theyellow light beam YLs in the light source device 2 according to thefirst embodiment, it is possible to increase the light intensity of thewhole of the green light which enters the pixel PX. Thus, it is possibleto increase the luminosity factor of the projection image.

It should be noted that it is possible to use a dichroic mirror having acharacteristic of reflecting the green light beam GLs and transmittingthe red light beam RLs as the third color separation element 35 incontrast to the present embodiment. Depending on the yellow phosphorincluded in the wavelength conversion element 28, the red light beamincluded in the yellow light beam YL emitted from the wavelengthconversion element 28 becomes insufficient in some cases. In this case,by using a dichroic mirror having the characteristic described above, itis possible to make the red light beam enter the first sub-pixel SX1 andthe third sub-pixel SX3 out of the four sub-pixels SX1 through SX4.Thus, it is possible to increase the color reproducibility of theprojection image.

Third Embodiment

A third embodiment of the present disclosure will hereinafter bedescribed using FIG. 10 through FIG. 13.

A light source device according to the third embodiment is substantiallythe same in basic configuration as that of the first embodiment, but isdifferent in arrangement and configuration of a variety of elements fromthat of the first embodiment. Therefore, the overall description of thelight source device will be omitted.

FIG. 10 is a plan view of a light source device 13 according to thethird embodiment viewed from the +Y direction. FIG. 11 is a side view ofthe light source device 13 viewed from the −X direction. FIG. 12 is aside view of the light source device 13 viewed from the +X direction.FIG. 13 is a schematic diagram showing positions of incidence of coloredlight beams on a multi-lens.

In FIG. 10 through FIG. 13, the constituents common to the drawings usedin the first embodiment are denoted by the same reference symbols, andthe description thereof will be omitted.

As shown in FIG. 10, the light source device 13 according to the presentembodiment is provided with the light source section 21, a firstpolarization split element 71, a first optical element 72, a secondpolarization split element 73, a second optical element 74, the firstretardation element 24, the first light collection element 25, thediffusion device 26, the second light collection element 27, thewavelength conversion element 28, the first color separation element 29,the fourth retardation element 32, the second color separation element33, the reflecting element 31, and the fifth retardation element 30.

In the light source device 13 according to the present embodiment, thepositions of the diffusion device 26 and the wavelength conversionelement 28 with respect to the first polarization split element 71 andthe first optical element 72 are reversed from the positions of thediffusion device 26 and the wavelength conversion element 28 withrespect to the first polarization split element 51 and the first opticalelement 52 in the first embodiment. In other words, in the light sourcedevice 13 according to the present embodiment, the wavelength conversionelement 28 is disposed at the −Z direction side of the firstpolarization split element 71. Further, the diffusion device 26 isdisposed at the −Z direction side of the first optical element 72.

Further, in the light source device 13 according to the presentembodiment, the positions of the second polarization split element 73and the second optical element 74 are reversed from the positions of thesecond polarization split element 23 and the second optical element 22in the first embodiment. Specifically, in the light source device 13according to the present embodiment, the second polarization splitelement 73 is disposed at the −X direction side of the second opticalelement 74. Further, in the light source device 13 according to thepresent embodiment, the positions of the first color separation element29 and the second color separation element 33 are reversed from thepositions of the first color separation element 29 and the second colorseparation element 33 in the first embodiment. Specifically, in thelight source device 13 according to the present embodiment, the firstcolor separation element 29 is disposed at the +X direction side of thesecond color separation element 33.

Configuration of First Polarization Split Element

The first polarization split element 71 transmits the blue light beamBLp as the P-polarized light which enters the first polarization splitelement 71 along the +X direction from the light source section 21toward the +X direction, and reflects the blue light beam BLs as theS-polarized light which enters the first polarization split element 71along the +X direction toward the −Z direction. Further, the yellowlight beam YL which enters the first polarization split element 71 alongthe +Z direction from the wavelength conversion element 28 istransmitted by the first polarization split element 71 toward the +Zdirection. Therefore, in the case of the present embodiment, the firstpolarization split element 71 has a polarization split characteristic oftransmitting the P-polarized light and reflecting the S-polarized lightwith respect to the light in the blue wavelength band, and acharacteristic of transmitting the light in the wavelength bandincluding the green wavelength band and the red wavelength bandirrespective of the polarization direction.

Configuration of First Optical Element

The first optical element 72 is disposed at the +X direction side of thefirst polarization split element 71. The blue light beam BLs whichenters the first optical element 72 along the +X direction from thefirst polarization split element 71 via the third retardation element 54is reflected by the first optical element 72 toward the −Z direction.Further, the blue light beam BLp which enters the first optical element72 along the +Z direction from the diffusion plate 261 is transmitted bythe first optical element 72 toward the +Z direction. Therefore, in thecase of the present embodiment, the first optical element 72 has apolarization split characteristic of transmitting the P-polarized lightand reflecting the S-polarized light with respect to the light in theblue wavelength band. Since the yellow light beam YL does not enter thefirst optical element 72, the characteristic of the first opticalelement 72 with respect to the light in the wavelength band includingthe green wavelength band and the red wavelength band is notparticularly limited.

It should be noted that it is described in the first embodiment that thethird retardation element 54 can be disposed and is not required to bedisposed, but in the present embodiment, the third retardation element54 is required to be disposed. The reason is that the blue light beamBLp having been transmitted through the first polarization split element71 is required to become the S-polarized light at the time point whenentering the first optical element 72 since the first optical element 72reflects the blue light beam BLs from the first polarization splitelement 71, and transmits the blue light beam BLp from the diffusionplate 261.

Configuration of Second Polarization Split Element

The second polarization split element 73 is disposed at the +Z directionside of the first polarization split element 71. The yellow light beamYL enters the second polarization split element 73 along the +Zdirection from the first polarization split element 71, and the secondpolarization split element 73 transmits the yellow light beam YLp as theP-polarized light toward the +Z direction, and reflects the yellow lightbeam YLs as the S-polarized light toward the +X direction. Therefore, inthe case of the present embodiment, the second polarization splitelement 73 has a polarization split characteristic of transmitting theP-polarized light and reflecting the S-polarized light with respect tothe light in the wavelength band including the green wavelength band andthe red wavelength band. Since the blue light beams BLp, BLs do notenter the second polarization split element 73, the characteristic withrespect to the blue light beams BLp, BLs of the second polarizationsplit element 73 is not particularly limited.

Configuration of Second Optical Element

The second optical element 74 is disposed at the +X direction side ofthe second polarization split element 73. Further, the second opticalelement 74 is disposed at the +Z direction side of the first opticalelement 72. The yellow light beam YLs as the S-polarized light whichenters the second optical element 74 along the +X direction from thesecond polarization split element 73 is reflected by the second opticalelement 74 toward the +Z direction. Further, the blue light beam BLpwhich enters the second optical element 74 along the +Z direction fromthe first optical element 72 is transmitted by the second opticalelement 74 toward the +Z direction. In the case of the presentembodiment, the second optical element 74 has a characteristic oftransmitting the P-polarized light with respect to the light in the bluewavelength band, and a characteristic of reflecting the S-polarizedlight with respect to the light in the wavelength band including thegreen wavelength band and the red wavelength band. Therefore, the secondoptical element 74 can be formed of a dichroic mirror for transmittingthe light in the blue wavelength band, and reflecting the light in thewavelength band including the green wavelength band and the redwavelength band irrespective of the polarization direction.

Configuration of Wavelength Conversion Element

The wavelength conversion element 28 is disposed at the −Z directionside of the first polarization split element 71. The second lightcollection element 27 is disposed between the first polarization splitelement 71 and the wavelength conversion element 28 on the Z axis.

The yellow light beam YL emitted from the wavelength conversion element28 is transmitted through the second light collection element 27 alongthe +Z direction, and is then transmitted through the first polarizationsplit element 71. Out of the yellow light beam YL as the unpolarizedlight which has been transmitted through the first polarization splitelement 71 to enter the second polarization split element 73, the yellowlight beam YLs as the S-polarized light is reflected by the polarizationsplit layer 731 toward the +X direction, and is then emitted from thesecond polarization split element 73. The yellow light beam YLs as theS-polarized light emitted along the +X direction from the secondpolarization split element 73 is reflected toward the +Z direction by anoptical layer 741 of the second optical element 74, and then enters thefirst color separation element 29.

Meanwhile, out of the yellow light beam YL as the unpolarized lighthaving entered the second polarization split element 73, the yellowlight beam YLp as the P-polarized light is transmitted through thepolarization split layer 731 toward the +Z direction to enter the secondcolor separation element 33 via the fourth retardation element 32.

Configuration of Diffusion Device

The diffusion device 26 is disposed at the −Z direction side of thefirst optical element 72. The first retardation element 24 is disposedbetween the first optical element 72 and the diffusion plate 261 on theZ axis. The blue light beams BLs as the S-polarized light enters thefirst retardation element 24 along the −Z direction from the firstoptical element 72. The first light collection element 25 is disposedbetween the first retardation element 24 and the diffusion plate 261 onthe Z axis.

The blue light beam BLs as the S-polarized light emitted from the thirdretardation element 54 is reflected by the first optical element 72 tobe converted by the first retardation element 24 into the blue lightbeam BLc1 as the circularly polarized light. The blue light beam BLc1having entered the diffusion plate 261 is reflected by the diffusionplate 261 to thereby be converted into the blue light beam BLc2 as thecircularly polarized light having an opposite rotational direction. Theblue light beam BLc2 emitted from the diffusion device 26 reenters thefirst retardation element 24 to be converted into the blue light beamBLp as the P-polarized light. The blue light beam BLp as the P-polarizedlight is transmitted through the first optical element 72 and the secondoptical element 74 toward the +Z direction, and then enters the firstcolor separation element 29.

Configuration of First Color Separation Element

As shown in FIG. 12, the first color separation element 29 is disposedat the +Z direction side of the second optical element 74. Theconfiguration of the first color separation element 29 is substantiallythe same as the configuration of the first color separation element 29in the first embodiment.

Configuration of Second Color Separation Element

As shown in FIG. 11, the second color separation element 33 is disposedat the +Z direction side of the second polarization split element 73.The configuration of the second color separation element 33 issubstantially the same as the configuration of the second colorseparation element 33 in the first embodiment.

In the case of the present embodiment, as shown in FIG. 13, the redlight beam RLs, the green light beam GLs, the yellow light beam YLs, andthe blue light beam BLs emitted from the light source device 13 enterthe first multi-lens 41. The red light beam RLs enters the plurality oflenses 411 included in the area A1 at the −X direction side and at the+Y direction side in the first multi-lens 41. The green light beam GLsenters the plurality of lenses 411 included in the area A2 at the −Xdirection side and at the −Y direction side in the first multi-lens 41.The yellow light beam YLs enters the plurality of lenses 411 included inthe area A3 at the +X direction side and at the +Y direction side in thefirst multi-lens 41. The blue light beam BLs enters the plurality oflenses 411 included in the area A4 at the +X direction side and at the−Y direction side in the first multi-lens 41.

The rest of the configuration of the light source device 13 and theprojector 1 is substantially the same as in the first embodiment.

Advantages of Third Embodiment

The light source device 13 according to the present embodiment isprovided with the light source section 21 which emits the blue lightbeams BLp, BLs having the blue wavelength band and respectivelyincluding the P-polarized light and the S-polarized light, the firstpolarization split element 71 which transmits the blue light beam BLp asthe P-polarized light entering the first polarization split element 71along the +X direction from the light source section 21 toward the +Xdirection, and reflects the blue light beam BLs as the S-polarized lighttoward the −Z direction crossing the +X direction, the first opticalelement 72 which is disposed at the +X direction side of the firstpolarization split element 71, and reflects the blue light beam BLsentering the first optical element 72 along the +X direction from thefirst polarization split element 71 toward the −Z direction, thediffusion plate 261 which is disposed at the −Z direction side of thefirst optical element 72, diffuses the blue light beam BLc1 entering thediffusion plate 261 along the −Z direction from the first opticalelement 72, and emits the blue light beam BLc2 thus diffused toward the+Z direction as an opposite direction to the −Z direction, thewavelength conversion element 28 which is disposed at the −Z directionside of the first polarization split element 71, performs the wavelengthconversion on the blue light beam BLs entering the wavelength conversionelement 28 along the −Z direction from the first polarization splitelement 71 to emit the yellow light beam YL having the wavelength banddifferent from the blue wavelength band toward the +Z direction, thesecond polarization split element 73 which is disposed at the +Zdirection side of the first polarization split element 71, which theyellow light beam YL enters along the +Z direction from the firstpolarization split element 71, and which transmits the yellow light beamYLp as the P-polarized light toward the +Z direction, and reflects theyellow light beam YLs as the S-polarized light toward the +X direction,and the second optical element 74 which is disposed at the +X directionside of the second polarization split element 73, and reflects theyellow light beam YLs as the S-polarized light entering the secondoptical element 74 along the +X direction from the second polarizationsplit element 73 toward the +Z direction, wherein the blue light beamBLp which enters the first optical element 72 along the +Z directionfrom the diffusion plate 261 is transmitted by the first optical element72 toward the +Z direction, the yellow light beam YL which enters thefirst polarization split element 71 along the +Z direction from thewavelength conversion element 28 is transmitted by the firstpolarization split element 71 toward the +Z direction, and the bluelight beam BLp which enters the second optical element 74 along the +Zdirection from the first optical element 72 is transmitted by the secondoptical element 74 toward the +Z direction.

Also in the present embodiment, it is possible to obtain substantiallythe same advantages as in the first embodiment such as the advantagethat it is possible to realize the light source device 13 capable ofemitting the plurality of colored light beams made uniform inpolarization direction without using the polarization conversion elementnarrow in pitch, the advantage that it is possible to achieve thereduction in size of the light source device 13 and the projector 1, andthe advantage that it is easy to form the dielectric multilayer film,and it is possible to manufacture the optical element and thepolarization split element which are low in cost, and excellent in lightseparation characteristic.

Further, the light source device 13 according to the present embodimentis further provided with the first retardation element 24 which isdisposed between the first optical element 72 and the diffusion plate261, and which the blue light beam BLs as the S-polarized light entersalong the −Z direction from the first optical element.

According to this configuration, it is possible to convert the bluelight beam BLc2 as the circularly polarized light having been emittedfrom the diffusion plate 261 with the first retardation element 24 intothe blue light beam BLp as the P-polarized light, and make the result betransmitted through the first optical element 72 and the second opticalelement 74. Thus, it is possible to increase the use efficiency of theblue light beam BLc2 emitted from the diffusion plate 261.

Further, the light source device 13 according to the present embodimentis further provided with the third retardation element 54 which isdisposed between the first polarization split element 71 and the firstoptical element 72, and converts the blue light beam BLp as theP-polarized light emitted along the +X direction from the firstpolarization split element 71 into the blue light beam BLs as theS-polarized light.

According to this configuration, it is possible to use an opticalelement which has the polarization split characteristic of transmittingthe blue light beam BLp as the P-polarized light and reflecting the bluelight beam BLs as the S-polarized light as the first optical element 72.Therefore, the configuration of the dielectric multilayer filmconstituting the first optical element 72 becomes simple, and theformation thereof becomes easy.

Fourth Embodiment

A fourth embodiment of the present disclosure will hereinafter bedescribed using FIG. 14 and FIG. 15.

A light source device according to the fourth embodiment issubstantially the same in basic configuration as that of the thirdembodiment, but is different in configuration of the reflecting elementfrom that of the third embodiment. Therefore, the overall description ofthe light source device will be omitted.

FIG. 14 is a side view of a light source device 14 according to thefourth embodiment viewed from the +X direction. FIG. 15 is a schematicdiagram showing positions of incidence of colored light beams on amulti-lens. In FIG. 14 and FIG. 15, the constituents common to thedrawings used in the third embodiment are denoted by the same referencesymbols, and the description thereof will be omitted.

As shown in FIG. 14, the light source device 14 according to the presentembodiment is provided with a third color separation element 35 insteadof the reflecting element in the light source device 13 according to thethird embodiment. Specifically, the third color separation element 35 isdisposed at the +Z direction side of the dichroic prism 291 on the lightpath of the yellow light beam YLs separated by the first colorseparation element 29. The third color separation element 35 is formedof a dichroic mirror having a characteristic of transmitting a greenlight beam GLs2 and reflecting the red light beam RLs. It should benoted that it is also possible to use a dichroic prism as the thirdcolor separation element 35 instead of the dichroic mirror.

Therefore, the green light beam GLs2 included in the yellow light beamYLs which enters the third color separation element 35 from the dichroicprism 291 of the first color separation element 29 is transmittedthrough the third color separation element 35 to be transmitted outsidethe light source device 14. In other words, the light source device 14according to the present embodiment emits the green light beam GLs2instead of the yellow light beam YLs from the position where the yellowlight beam YLs is emitted in the light source device 13 according to thethird embodiment.

Meanwhile, the red light beam RLs included in the yellow light beam YLswhich enters the third color separation element 35 is reflected by thethird color separation element 35 to enter the second optical element 74from the −Z direction. The red light beam RLs returns to the wavelengthconversion element 28 via the second polarization split element 73, thefirst polarization split element 71, and the second light collectionelement 27. The behavior of the red light beam RLs having returned tothe wavelength conversion element 28 is substantially the same as in thesecond embodiment.

As shown in FIG. 15, the light source device 14 emits the red light beamRLs, the green light beam GLs, the green light beam GLs2, and the bluelight beam BLs. The green light beam GLs2 is emitted from the positionat the +X direction side and at the +Y direction side in the lightsource device 14, and then enters the plurality of lenses 411 disposedin the area A3 located at the +X direction side and at the +Y directionside in the first multi-lens 41. The green light beam GLs2 enters themicrolenses 621 via the first multi-lens 41, the second multi-lens 42,the superimposing lens 43, and the field lens 5 similarly to the yellowlight beam YLs in the third embodiment. The green light beam GLs2 havingentered each of the microlenses 621 enters the third sub-pixel SX3 ofthe pixel PX corresponding to that microlens 621.

Advantages of Fourth Embodiment

Also in the present embodiment, it is possible to obtain substantiallythe same advantages as in the first embodiment such as the advantagethat it is possible to realize the light source device 14 capable ofemitting the plurality of colored light beams made uniform inpolarization direction without using the polarization conversion elementnarrow in pitch, the advantage that it is possible to achieve thereduction in size of the light source device 14 and the projector 1, andthe advantage that it is easy to form the dielectric multilayer film,and it is possible to manufacture the optical element and thepolarization split element which are low in cost, and excellent in lightseparation characteristic.

Further, in the light source device 14 according to the presentembodiment, since the green light beam GLs2 is emitted instead of theyellow light beam YLs in the light source device 13 according to thethird embodiment, it is possible to increase the light intensity of thewhole of the green light which enters the pixel PX. Thus, it is possibleto increase the luminosity factor of the projection image.

It should be noted that it is possible to use a dichroic mirror having acharacteristic of reflecting the green light beam GLp and transmittingthe red light beam RLp as the third color separation element 35 incontrast to the present embodiment. In this case, by using a dichroicmirror having the characteristic described above, it is possible to makethe red light beam enter the second sub-pixel SX2 and the fourthsub-pixel SX4 out of the four sub-pixels SX1 through SX4. Thus, it ispossible to increase the color reproducibility of the projection image.

It should be noted that the scope of the present disclosure is notlimited to the embodiments described above, but a variety ofmodifications can be provided thereto within the scope or the spirit ofthe present disclosure.

For example, in each of the embodiments, each of the first polarizationsplit elements 51, 71, the first optical elements 52, 72, the secondpolarization split elements 23, 73, and the second optical elements 22,74 can be formed of a plate type optical element, or can be formed of aprism type optical element.

In each of the embodiments described above, the light source device isprovided with the first light collection element 25 and the second lightcollection element 27. However, this configuration is not a limitation,and at least one of the first light collection element 25 and the secondlight collection element 27 is not required to be disposed.

In each of the embodiments described above, the light source section 21emits the blue light beams BLs, BLp toward the +X direction. However,this is not a limitation, and it is also possible to adopt aconfiguration in which the light source section 21 emits the blue lightbeams BLs, BLp in a direction crossing the +X direction, and the bluelight beams BLs, BLp are reflected using, for example, a reflectingmember, and are then made to enter the first polarization split element51 in the +X direction.

In each of the embodiments described above, the projector 1 is providedwith the homogenization device 4 having the first multi-lens 41, thesecond multi-lens 42, and the superimposing lens 43. It is possible todispose a homogenization device having other configurations instead ofthis configuration, or it is not required to dispose the homogenizationdevice 4.

The light source device according to each of the embodiments describedabove emits the colored light beams from the four exit positions,respectively, and the liquid crystal panel 61 constituting the lightmodulation device 6 has the four sub-pixels SX in each of the pixels PX.Instead of this configuration, it is possible to adopt a configurationin which the light source device emits three colored light beams, andthe liquid crystal panel has three sub-pixels in each pixel. In thiscase, for example, in the light source devices according to theembodiments described above, a total reflection member can be disposedin the light path of the yellow light beam YLs.

The light source device according to the first embodiment and the thirdembodiment emits the blue light beam BLs, the yellow light beam YLs, thegreen light beam GLs, and the red light beam RLs which are eachS-polarized light, and are spatially separated from each other. Further,the light source device according to the second embodiment and thefourth embodiment emits the blue light beam BLs, the green light beamGLs, and the red light beam RLs which are each S-polarized light, andare spatially separated from each other. Instead of theseconfigurations, the polarization state of the colored light beamsemitted by the light source device can be another polarization state.For example, it is possible for the light source device to have aconfiguration of emitting a plurality of colored light beams which areeach P-polarized light, and are spatially separated from each other.Further, the colored light beams emitted by the light source device arenot limited to the blue light beam, the yellow light beam, the greenlight beam, and the red light beam, but can also be other colored lightbeams. For example, the light source device can be provided with aconfiguration of emitting white light instead of the blue light and theyellow light.

Besides the above, the specific descriptions of the shape, the number,the arrangement, the material, and so on of the constituents of thelight source device and the projector are not limited to those of theembodiments described above, but can arbitrarily be modified. Further,although in the embodiments described above, there is described theexample of installing the light source device according to the presentdisclosure in the projector, the example is not a limitation. The lightsource device according to an aspect of the present disclosure can alsobe applied to lighting equipment, a headlight of a vehicle, and so on.

A light source device according to an aspect of the present disclosuremay have the following configuration.

The light source device according to one aspect of the presentdisclosure includes a light source section configured to emit a firstlight beam which has a first wavelength band and includes lightpolarized in a first polarization direction and light polarized in asecond polarization direction different from the first polarizationdirection, a first polarization split element which is configured totransmit the first light beam entering the first polarization splitelement from the light source section along a first direction andpolarized in the first polarization direction toward the firstdirection, and is configured to reflect the first light beam polarizedin the second polarization direction toward a second direction crossingthe first direction, a first optical element disposed at the firstdirection side of the first polarization split element, and configuredto reflect the first light beam which enters the first optical elementalong the first direction from the first polarization split elementtoward the second direction, a diffusion element disposed at the seconddirection side of the first polarization split element, and configuredto diffuse the first light beam which enters the diffusion element alongthe second direction from the first polarization split element, and emitthe first light beam diffused toward a third direction as an oppositedirection to the second direction, a wavelength conversion elementdisposed at the second direction side of the first optical element,configured to perform wavelength conversion on the first light beamwhich enters the wavelength conversion element along the seconddirection from the first optical element, and configured to emit asecond light beam having a second wavelength band different from thefirst wavelength band toward the third direction, a second polarizationsplit element which is disposed at the third direction side of the firstoptical element, which the second light beam enters along the thirddirection from the first optical element, and which is configured totransmit the second light beam polarized in the first polarizationdirection toward the third direction, and reflect the second light beampolarized in the second polarization direction toward a fourth directionas an opposite direction to the first direction, and a second opticalelement disposed at the fourth direction side of the second polarizationsplit element, and configured to reflect the second light beam whichenters the second optical element along the fourth direction from thesecond polarization split element, and is polarized in the secondpolarization direction, toward the third direction, wherein the firstpolarization split element transmits the first light beam which entersthe first polarization split element along the third direction from thediffusion element toward the third direction, the first optical elementtransmits the second light beam which enters the first optical elementalong the third direction from the wavelength conversion element towardthe third direction, and the second optical element transmits the firstlight beam which enters the second optical element along the thirddirection from the first polarization split element toward the thirddirection.

In the light source device according to the one aspect of the presentdisclosure, there may further be included a first retardation elementwhich is disposed between the first polarization split element and thediffusion element, and which the first light beam emitted along thesecond direction from the first polarization split element enters.

A light source device according to another aspect of the presentdisclosure includes a light source section configured to emit a firstlight beam which has a first wavelength band and includes lightpolarized in a first polarization direction and light polarized in asecond polarization direction different from the first polarizationdirection, a first polarization split element which is configured totransmit the first light beam entering the first polarization splitelement from the light source section along a first direction andpolarized in the first polarization direction toward the firstdirection, and is configured to reflect the first light beam polarizedin the second polarization direction toward a second direction crossingthe first direction, a first optical element disposed at the firstdirection side of the first polarization split element, and configuredto reflect the first light beam which enters the first optical elementalong the first direction from the first polarization split elementtoward the second direction, a diffusion element disposed at the seconddirection side of the first optical element, and configured to diffusethe first light beam which enters the diffusion element along the seconddirection from the first optical element, and emit the first light beamdiffused toward a third direction as an opposite direction to the seconddirection, a wavelength conversion element disposed at the seconddirection side of the first polarization split element, configured toperform wavelength conversion on the first light beam which enters thewavelength conversion element along the second direction from the firstpolarization split element, and configured to emit a second light beamhaving a second wavelength band different from the first wavelength bandtoward the third direction, a second polarization split element which isdisposed at the third direction side of the first polarization splitelement, which the second light beam enters along the third directionfrom the first polarization split element, and which is configured totransmit the second light beam polarized in the first polarizationdirection toward the third direction, and reflect the second light beampolarized in the second polarization direction toward the firstdirection, and a second optical element disposed at the first directionside of the second polarization split element, and configured to reflectthe second light beam which enters the second optical element along thefirst direction from the second polarization split element, and ispolarized in the second polarization direction, toward the thirddirection, wherein the first optical element transmits the first lightbeam which enters the first optical element along the third directionfrom the diffusion element toward the third direction, the firstpolarization split element transmits the second light beam which entersthe first polarization split element along the third direction from thewavelength conversion element toward the third direction, and the secondoptical element transmits the first light beam which enters the secondoptical element along the third direction from the first optical elementtoward the third direction.

In the light source device according to the another aspect of thepresent disclosure, there may further be included a first retardationelement which is disposed between the first optical element and thediffusion element, and which the first light beam emitted along thesecond direction from the first optical element and polarized in thesecond polarization direction enters.

In the light source device according to the another aspect of thepresent disclosure, there may further be included a third retardationelement disposed between the first polarization split element and thefirst optical element, and configured to convert the first light beamwhich is emitted along the first direction from the first polarizationsplit element and is polarized in the first polarization direction intothe first light beam polarized in the second polarization direction.

In the light source device according to the one aspect of the presentdisclosure, or the light source device according to the another aspectof the present disclosure, the light source section may include a lightemitting element configured to emit light having the first wavelengthband, and a second retardation element which the light having the firstwavelength band emitted from the light emitting element enters, andwhich is configured to emit the first light beam including lightpolarized in the first polarization direction and light polarized in thesecond polarization direction.

In the light source device according to the one aspect of the presentdisclosure, or the light source device according to the another aspectof the present disclosure, the second retardation element may be maderotatable around a rotational axis along a proceeding direction of thelight entering the second retardation element.

In the light source device according to the one aspect of the presentdisclosure, or the light source device according to the another aspectof the present disclosure, there may further be included a first colorseparation element disposed at the third direction side of the secondoptical element, and configured to separate light emitted from thesecond optical element into a third light beam having the firstwavelength band and a fourth light beam having the second wavelengthband, and a second color separation element disposed at the thirddirection side of the second polarization split element, and configuredto separate light emitted from the second polarization split elementinto a fifth light beam having a third wavelength band different fromthe second wavelength band, and a sixth light beam having a fourthwavelength band different from the second wavelength band and the thirdwavelength band.

A projector according to an aspect of the present disclosure may havethe following configuration.

The projector according to the aspect of the present disclosure includesthe light source device according to the one aspect of the presentdisclosure, a light modulation device configured to modulate light fromthe light source device in accordance with image information, and aprojection optical device configured to project the light modulated bythe light modulation device.

In the projector according to the aspect of the present disclosure,there may further be included a homogenization device disposed betweenthe light source device and the light modulation device, wherein thehomogenization device may include a pair of multi-lenses configured todivide the light entering the pair of multi-lenses from the light sourcedevice into a plurality of partial light beams, and a superimposing lensconfigured to superimpose the plurality of partial light beams enteringthe superimposing lens from the pair of multi-lenses on the lightmodulation device.

In the projector according to the aspect of the present disclosure, thelight modulation device may include a liquid crystal panel having aplurality of pixels, and a microlens array which is disposed at a lightincident side of the liquid crystal panel, and has a plurality ofmicrolenses corresponding to the plurality of pixels, the pixels mayeach include a first sub-pixel, a second sub-pixel, a third sub-pixel,and a fourth sub-pixel, and the microlens may make the third light beamenter the second sub-pixel, the fourth light beam enter the firstsub-pixel, the fifth light beam enter the fourth sub-pixel, and thesixth light beam enter the third sub-pixel.

What is claimed is:
 1. A light source device comprising: a light sourcesection configured to emit a first light beam which has a firstwavelength band and includes light polarized in a first polarizationdirection and light polarized in a second polarization directiondifferent from the first polarization direction; a first polarizationsplit element which is configured to transmit the first light beamentering the first polarization split element from the light sourcesection along a first direction and polarized in the first polarizationdirection toward the first direction, and is configured to reflect thefirst light beam polarized in the second polarization direction toward asecond direction crossing the first direction; a first optical elementdisposed at the first direction side of the first polarization splitelement, and configured to reflect the first light beam which enters thefirst optical element along the first direction from the firstpolarization split element toward the second direction; a diffusionelement disposed at the second direction side of the first polarizationsplit element, and configured to diffuse the first light beam whichenters the diffusion element along the second direction from the firstpolarization split element, and emit the first light beam diffusedtoward a third direction as an opposite direction to the seconddirection; a wavelength conversion element disposed at the seconddirection side of the first optical element, configured to performwavelength conversion on the first light beam which enters thewavelength conversion element along the second direction from the firstoptical element, and configured to emit a second light beam having asecond wavelength band different from the first wavelength band towardthe third direction; a second polarization split element which isdisposed at the third direction side of the first optical element, whichthe second light beam enters along the third direction from the firstoptical element, and which is configured to transmit the second lightbeam polarized in the first polarization direction toward the thirddirection, and reflect the second light beam polarized in the secondpolarization direction toward a fourth direction as an oppositedirection to the first direction; and a second optical element disposedat the fourth direction side of the second polarization split element,and configured to reflect the second light beam which enters the secondoptical element along the fourth direction from the second polarizationsplit element, and is polarized in the second polarization direction,toward the third direction, wherein the first polarization split elementtransmits the first light beam which enters the first polarization splitelement along the third direction from the diffusion element toward thethird direction, the first optical element transmits the second lightbeam which enters the first optical element along the third directionfrom the wavelength conversion element toward the third direction, andthe second optical element transmits the first light beam which entersthe second optical element along the third direction from the firstpolarization split element toward the third direction.
 2. The lightsource device according to claim 1, further comprising: a firstretardation element which is disposed between the first polarizationsplit element and the diffusion element, and which the first light beamemitted along the second direction from the first polarization splitelement enters.
 3. A light source device comprising: a light sourcesection configured to emit a first light beam which has a firstwavelength band and includes light polarized in a first polarizationdirection and light polarized in a second polarization directiondifferent from the first polarization direction; a first polarizationsplit element which is configured to transmit the first light beamentering the first polarization split element from the light sourcesection along a first direction and polarized in the first polarizationdirection toward the first direction, and is configured to reflect thefirst light beam polarized in the second polarization direction toward asecond direction crossing the first direction; a first optical elementdisposed at the first direction side of the first polarization splitelement, and configured to reflect the first light beam which enters thefirst optical element along the first direction from the firstpolarization split element toward the second direction; a diffusionelement disposed at the second direction side of the first opticalelement, and configured to diffuse the first light beam which enters thediffusion element along the second direction from the first opticalelement, and emit the first light beam diffused toward a third directionas an opposite direction to the second direction; a wavelengthconversion element disposed at the second direction side of the firstpolarization split element, configured to perform wavelength conversionon the first light beam which enters the wavelength conversion elementalong the second direction from the first polarization split element,and configured to emit a second light beam having a second wavelengthband different from the first wavelength band toward the thirddirection; a second polarization split element which is disposed at thethird direction side of the first polarization split element, which thesecond light beam enters along the third direction from the firstpolarization split element, and which is configured to transmit thesecond light beam polarized in the first polarization direction towardthe third direction, and reflect the second light beam polarized in thesecond polarization direction toward the first direction; and a secondoptical element disposed at the first direction side of the secondpolarization split element, and configured to reflect the second lightbeam which enters the second optical element along the first directionfrom the second polarization split element, and is polarized in thesecond polarization direction, toward the third direction, wherein thefirst optical element transmits the first light beam which enters thefirst optical element along the third direction from the diffusionelement toward the third direction, the first polarization split elementtransmits the second light beam which enters the first polarizationsplit element along the third direction from the wavelength conversionelement toward the third direction, and the second optical elementtransmits the first light beam which enters the second optical elementalong the third direction from the first optical element toward thethird direction.
 4. The light source device according to claim 3,further comprising: a first retardation element which is disposedbetween the first optical element and the diffusion element, and whichthe first light beam emitted along the second direction from the firstoptical element and polarized in the second polarization directionenters.
 5. The light source device according to claim 3, furthercomprising: a third retardation element disposed between the firstpolarization split element and the first optical element, and configuredto convert the first light beam which is emitted along the firstdirection from the first polarization split element and is polarized inthe first polarization direction into the first light beam polarized inthe second polarization direction.
 6. The light source device accordingto claim 1, wherein the light source section includes a light emittingelement configured to emit light having the first wavelength band, and asecond retardation element which the light having the first wavelengthband emitted from the light emitting element enters, and which isconfigured to emit the first light beam including light polarized in thefirst polarization direction and light polarized in the secondpolarization direction.
 7. The light source device according to claim 6,wherein the second retardation element is made rotatable around arotational axis along a proceeding direction of the light entering thesecond retardation element.
 8. The light source device according toclaim 1, further comprising: a first color separation element disposedat the third direction side of the second optical element, andconfigured to separate light emitted from the second optical elementinto a third light beam having the first wavelength band and a fourthlight beam having the second wavelength band; and a second colorseparation element disposed at the third direction side of the secondpolarization split element, and configured to separate light emittedfrom the second polarization split element into a fifth light beamhaving a third wavelength band different from the second wavelengthband, and a sixth light beam having a fourth wavelength band differentfrom the second wavelength band and the third wavelength band.
 9. Aprojector comprising: the light source device according to claim 1; alight modulation device configured to modulate light from the lightsource device in accordance with image information; and a projectionoptical device configured to project the light modulated by the lightmodulation device.
 10. The projector according to claim 9, furthercomprising: a homogenization device disposed between the light sourcedevice and the light modulation device, wherein the homogenizationdevice includes a pair of multi-lenses configured to divide the lightentering the pair of multi-lenses from the light source device into aplurality of partial light beams, and a superimposing lens configured tosuperimpose the plurality of partial light beams entering thesuperimposing lens from the pair of multi-lenses on the light modulationdevice.
 11. The projector according to claim 10, wherein the lightmodulation device includes a liquid crystal panel having a plurality ofpixels, and a microlens array which is disposed at a light incident sideof the liquid crystal panel, and has a plurality of microlensescorresponding to the plurality of pixels, the pixels each include afirst sub-pixel, a second sub-pixel, a third sub-pixel, and a fourthsub-pixel, and the microlens makes the third light beam enter the secondsub-pixel, the fourth light beam enter the first sub-pixel, the fifthlight beam enter the fourth sub-pixel, and the sixth light beam enterthe third sub-pixel.